diff --git a/lib/Slic3r.pm b/lib/Slic3r.pm
index 9f2cc213..a8fbbdb0 100644
--- a/lib/Slic3r.pm
+++ b/lib/Slic3r.pm
@@ -26,7 +26,7 @@ use Slic3r::Surface;
 use Slic3r::Surface::Collection;
 
 # printer options
-our $nozzle_diameter    = 0.45;
+our $nozzle_diameter    = 0.5;
 our $print_center       = [100,100];  # object will be centered around this point
 our $use_relative_e_distances = 0;
 our $z_offset = 0;
@@ -38,11 +38,12 @@ our $filament_packing_density = 0.85;
 # speed options
 our $print_feed_rate            = 60;   # mm/sec
 our $travel_feed_rate           = 130;   # mm/sec
-our $bottom_layer_speed_ratio   = 0.6;
+our $bottom_layer_speed_ratio   = 0.3;
 
 # accuracy options
 our $resolution         = 0.001;
 our $layer_height       = 0.4;
+our $thickness_ratio    = 1;
 our $flow_width;
 
 # print options
@@ -50,10 +51,10 @@ our $perimeter_offsets  = 3;
 our $solid_layers       = 3;
 our $fill_density       = 0.4;  # 1 = 100%
 our $fill_angle         = 0;
-our $temperature        = 195;
+our $temperature        = 200;
 
 # retraction options
-our $retract_length         = 2;    # mm
+our $retract_length         = 1;    # mm
 our $retract_restart_extra  = 0;    # mm
 our $retract_speed          = 40;   # mm/sec
 
diff --git a/lib/Slic3r/Extruder.pm b/lib/Slic3r/Extruder.pm
index 23ff0eac..ce7015d8 100644
--- a/lib/Slic3r/Extruder.pm
+++ b/lib/Slic3r/Extruder.pm
@@ -87,10 +87,9 @@ sub extrude {
         # calculate how much filament to drive into the extruder
         # to get the desired amount of extruded plastic
         my $e = $line->a->distance_to($line->b) * $Slic3r::resolution
-            * $Slic3r::flow_width 
-            * $Slic3r::layer_height
-            / (($Slic3r::filament_diameter ** 2) * PI)
-            / $Slic3r::filament_packing_density;
+            * (($Slic3r::nozzle_diameter**2) / ($Slic3r::filament_diameter ** 2))
+            * $Slic3r::thickness_ratio 
+            * $Slic3r::filament_packing_density;
         
         $gcode .= $self->G1($line->b, undef, $e, $description);
     }
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index 615ec914..b97a214f 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -165,7 +165,7 @@ sub export_gcode {
     # write start commands to file
     # TODO: this must be customizable by user
     print  $fh "G28 ; home all axes\n";
-    printf $fh "M109 S%d ; wait for temperature to be reached\n", $Slic3r::temperature;
+    printf $fh "M104 S%d ; wait for temperature to be reached\n", $Slic3r::temperature;
     print  $fh "G90 ; use absolute coordinates\n";
     print  $fh "G21 ; set units to millimeters\n";
     if ($Slic3r::use_relative_e_distances) {
diff --git a/slic3r.pl b/slic3r.pl
index eb3944c2..a112baf8 100755
--- a/slic3r.pl
+++ b/slic3r.pl
@@ -13,6 +13,8 @@ use Slic3r;
 use Time::HiRes qw(gettimeofday tv_interval);
 use XXX;
 
+use constant PI => 4 * atan2(1, 1);
+
 my %opt;
 GetOptions(
     'help'                  => sub { usage() },
@@ -78,7 +80,8 @@ GetOptions(
         if $Slic3r::nozzle_diameter < 0;
     die "--layer-height can't be greater than --nozzle-diameter\n"
         if $Slic3r::layer_height > $Slic3r::nozzle_diameter;
-    $Slic3r::flow_width = 4 * (($Slic3r::nozzle_diameter/2)**2) / $Slic3r::layer_height;
+    $Slic3r::flow_width = ($Slic3r::nozzle_diameter**2) 
+        * $Slic3r::thickness_ratio * PI / (4 * $Slic3r::layer_height);
     Slic3r::debugf "Flow width = $Slic3r::flow_width\n";
     
     # --perimeters