diff --git a/Build.PL b/Build.PL
index 75b74c51..650934dd 100644
--- a/Build.PL
+++ b/Build.PL
@@ -28,9 +28,15 @@ my %recommends = qw(
     Growl::GNTP                     0.15
     XML::SAX::ExpatXS               0
 );
-
-# removed:
-# Wx 0.9901
+if ($ARGV[0] eq '--gui') {
+    %prereqs = qw(
+    Wx                              0.9901
+    );
+    %recommends = qw(
+    Wx::GLCanvas                    0
+    OpenGL                          0
+    );
+}
 
 my $missing_prereqs = 0;
 if ($ENV{SLIC3R_NO_AUTO}) {
@@ -80,6 +86,9 @@ If it is installed in a non-standard location you can do:
 EOF
         if !$cpanm;
     
+    # make sure our cpanm is updated (old ones don't support the ~ syntax)
+    system $cpanm, 'App::cpanminus';
+    
     my %modules = (%prereqs, %recommends);
     foreach my $module (sort keys %modules) {
         my $version = $modules{$module};
diff --git a/lib/Slic3r/Config.pm b/lib/Slic3r/Config.pm
index a6f86e16..faa6fc06 100644
--- a/lib/Slic3r/Config.pm
+++ b/lib/Slic3r/Config.pm
@@ -6,7 +6,8 @@ use utf8;
 use List::Util qw(first);
 
 # cemetery of old config settings
-our @Ignore = qw(duplicate_x duplicate_y multiply_x multiply_y support_material_tool acceleration);
+our @Ignore = qw(duplicate_x duplicate_y multiply_x multiply_y support_material_tool acceleration
+    adjust_overhang_flow);
 
 my $serialize_comma     = sub { join ',', @{$_[0]} };
 my $serialize_comma_bool = sub { join ',', map $_ // 0, @{$_[0]} };
@@ -560,7 +561,7 @@ our $Options = {
         default => 70,
     },
     'extra_perimeters' => {
-        label   => 'Generate extra perimeters when needed',
+        label   => 'Extra perimeters if needed',
         tooltip => 'Add more perimeters when needed for avoiding gaps in sloping walls.',
         cli     => 'extra-perimeters!',
         type    => 'bool',
@@ -573,6 +574,34 @@ our $Options = {
         type    => 'bool',
         default => 0,
     },
+    'start_perimeters_at_concave_points' => {
+        label   => 'Concave points',
+        tooltip => 'Prefer to start perimeters at a concave point.',
+        cli     => 'start-perimeters-at-concave-points!',
+        type    => 'bool',
+        default => 0,
+    },
+    'start_perimeters_at_non_overhang' => {
+        label   => 'Non-overhang points',
+        tooltip => 'Prefer to start perimeters at non-overhanging points.',
+        cli     => 'start-perimeters-at-non-overhang!',
+        type    => 'bool',
+        default => 0,
+    },
+    'thin_walls' => {
+        label   => 'Detect thin walls',
+        tooltip => 'Detect single-width walls (parts where two extrusions don\'t fit and we need to collapse them into a single trace).',
+        cli     => 'thin-walls!',
+        type    => 'bool',
+        default => 1,
+    },
+    'overhangs' => {
+        label   => 'Detect overhangs',
+        tooltip => 'Experimental option to adjust flow for overhangs (bridge flow will be used), to apply bridge speed to them and enable fan.',
+        cli     => 'overhangs!',
+        type    => 'bool',
+        default => 1,
+    },
     'avoid_crossing_perimeters' => {
         label   => 'Avoid crossing perimeters',
         tooltip => 'Optimize travel moves in order to minimize the crossing of perimeters. This is mostly useful with Bowden extruders which suffer from oozing. This feature slows down both the print and the G-code generation.',
diff --git a/lib/Slic3r/GCode.pm b/lib/Slic3r/GCode.pm
index 403303d3..d4e498a9 100644
--- a/lib/Slic3r/GCode.pm
+++ b/lib/Slic3r/GCode.pm
@@ -155,9 +155,14 @@ sub extrude_loop {
     
     # find candidate starting points
     # start looking for concave vertices not being overhangs
-    my @concave = $loop->polygon->concave_points;
-    my @candidates = grep !Boost::Geometry::Utils::point_covered_by_multi_polygon($_, $self->_layer_overhangs),
-        @concave;
+    my @concave = ();
+    if ($Slic3r::Config->start_perimeters_at_concave_points) {
+        @concave = $loop->polygon->concave_points;
+    }
+    my @candidates = ();
+    if ($Slic3r::Config->start_perimeters_at_non_overhang) {
+        @candidates = grep !Boost::Geometry::Utils::point_covered_by_multi_polygon($_, $self->_layer_overhangs), @concave;
+    }
     if (!@candidates) {
         # if none, look for any concave vertex
         @candidates = @concave;
@@ -192,7 +197,7 @@ sub extrude_loop {
     
     my @paths = ();
     # detect overhanging/bridging perimeters
-    if ($extrusion_path->is_perimeter && @{$self->_layer_overhangs}) {
+    if ($Slic3r::Config->overhangs && $extrusion_path->is_perimeter && @{$self->_layer_overhangs}) {
         # get non-overhang paths by subtracting overhangs from the loop
         push @paths,
             $extrusion_path->subtract_expolygons($self->_layer_overhangs);
diff --git a/lib/Slic3r/GUI/Tab.pm b/lib/Slic3r/GUI/Tab.pm
index c985e93c..27ff3c56 100644
--- a/lib/Slic3r/GUI/Tab.pm
+++ b/lib/Slic3r/GUI/Tab.pm
@@ -398,7 +398,7 @@ sub build {
         },
         {
             title => 'Vertical shells',
-            options => [qw(perimeters randomize_start extra_perimeters)],
+            options => [qw(perimeters spiral_vase)],
         },
         {
             title => 'Horizontal shells',
@@ -410,9 +410,23 @@ sub build {
                 },
             ],
         },
+        {
+            title => 'Quality (slower slicing)',
+            options => [qw(extra_perimeters avoid_crossing_perimeters start_perimeters_at_concave_points start_perimeters_at_non_overhang thin_walls overhangs)],
+            lines => [
+                Slic3r::GUI::OptionsGroup->single_option_line('extra_perimeters'),
+                Slic3r::GUI::OptionsGroup->single_option_line('avoid_crossing_perimeters'),
+                {
+                    label   => 'Start perimeters at',
+                    options => [qw(start_perimeters_at_concave_points start_perimeters_at_non_overhang)],
+                },
+                Slic3r::GUI::OptionsGroup->single_option_line('thin_walls'),
+                Slic3r::GUI::OptionsGroup->single_option_line('overhangs'),
+            ],
+        },
         {
             title => 'Advanced',
-            options => [qw(avoid_crossing_perimeters external_perimeters_first spiral_vase)],
+            options => [qw(randomize_start external_perimeters_first)],
         },
     ]);
     
@@ -421,9 +435,13 @@ sub build {
             title => 'Infill',
             options => [qw(fill_density fill_pattern solid_fill_pattern)],
         },
+        {
+            title => 'Reducing printing time',
+            options => [qw(infill_every_layers infill_only_where_needed)],
+        },
         {
             title => 'Advanced',
-            options => [qw(infill_every_layers infill_only_where_needed solid_infill_every_layers fill_angle
+            options => [qw(solid_infill_every_layers fill_angle
                 solid_infill_below_area only_retract_when_crossing_perimeters infill_first)],
         },
     ]);
diff --git a/lib/Slic3r/Layer/Region.pm b/lib/Slic3r/Layer/Region.pm
index 8ab7a5a6..3b5bfe0d 100644
--- a/lib/Slic3r/Layer/Region.pm
+++ b/lib/Slic3r/Layer/Region.pm
@@ -96,7 +96,7 @@ sub make_surfaces {
     $self->slices([ _merge_loops($loops) ]);
     
     # detect thin walls by offsetting slices by half extrusion inwards
-    {
+    if ($Slic3r::Config->thin_walls) {
         my $width = $self->perimeter_flow->scaled_width;
         my $diff = diff_ex(
             [ map $_->p, @{$self->slices} ],
diff --git a/slic3r.pl b/slic3r.pl
index c46a8878..4a654b31 100755
--- a/slic3r.pl
+++ b/slic3r.pl
@@ -273,9 +273,7 @@ $j
                         home X axis [G28 X], disable motors [M84]).
     --layer-gcode       Load layer-change G-code from the supplied file (default: nothing).
     --toolchange-gcode  Load tool-change G-code from the supplied file (default: nothing).
-    --extra-perimeters  Add more perimeters when needed (default: yes)
     --randomize-start   Randomize starting point across layers (default: yes)
-    --avoid-crossing-perimeters Optimize travel moves so that no perimeters are crossed (default: no)
     --external-perimeters-first Reverse perimeter order. (default: no)
     --spiral-vase       Experimental option to raise Z gradually when printing single-walled vases
                         (default: no)
@@ -289,6 +287,17 @@ $j
                         Only infill under ceilings (default: no)
     --infill-first      Make infill before perimeters (default: no)
   
+   Quality options (slower slicing):
+    --extra-perimeters  Add more perimeters when needed (default: yes)
+    --avoid-crossing-perimeters Optimize travel moves so that no perimeters are crossed (default: no)
+    --start-perimeters-at-concave-points
+                        Try to start perimeters at concave points if any (default: no)
+    --start-perimeters-at-non-overhang
+                        Try to start perimeters at non-overhang points if any (default: no)
+    --thin-walls        Detect single-width walls (default: yes)
+    --overhangs         Experimental option to use bridge flow, speed and fan for overhangs
+                        (default: yes)
+  
    Support material options:
     --support-material  Generate support material for overhangs
     --support-material-threshold
diff --git a/t/perimeters.t b/t/perimeters.t
index 1ce91bd3..1dacd31c 100644
--- a/t/perimeters.t
+++ b/t/perimeters.t
@@ -73,6 +73,7 @@ use Slic3r::Test;
     }
     
     {
+        $config->set('start_perimeters_at_concave_points', 1);
         my $print = Slic3r::Test::init_print('L', config => $config);
         my $loop_starts_from_convex_point = 0;
         my $cur_loop;
@@ -102,6 +103,7 @@ use Slic3r::Test;
         $config->set('fan_below_layer_time', 0);
         $config->set('slowdown_below_layer_time', 0);
         $config->set('bridge_fan_speed', 100);
+        $config->set('overhangs', 1);
         my $print = Slic3r::Test::init_print('overhang', config => $config);
         my %layer_speeds = ();  # print Z => [ speeds ]
         my $fan_speed = 0;