Makerbot #453 : Homing in place

Last night I took some time to make my Start and End script for Skeinforge so I will not have to recenter my plastruder each time.
First, I was using G0 X100 Y100  to push the build plate at the end but I found that it took some time after reaching the endstop before doing the next steps. It took Much much longer time also with the G0 Z-50. It took about 2 minutes before doing next commands.
I found that G28 works better. No waiting time when reaching the endstop. I had to make some modification to my Z endstop triggers. I know it's not looking really good but it works. Next time I will make one in ABS with the possibility to adjust it.

(beginning of start.txt)

M104 S220 T0 (Extruder Temperature to 220 Celsius)

M109 S100 T0 (Heated Platform Temperature to 110 Celsius)

M107 (fan off)

G21 (Metric FTW)

G90 (Absolute Positioning)

G92 X0 Y0 Z0 (You are now at 0,0,0)

G0 Z5 ( Go higher to be safe)

G28 X0 Y0 ;go home ( XY at the MAX)

G28 Z0 ( Go down with Z)

G92 X0 Y0 Z0 (You are now at 0,0,0)

G0 Z1.5 (Higher a little bit to clear the place)

M6 T0 (Wait for tool to heat up)

G0 X57.5 Y45 (Put the build plate in the center)

G0 Z-1.5 (return to the base)

G92 X0 Y0 Z0 (You are now at 0,0,0)

(end of start.txt)

(beginning of end.txt)

(end of the file, cooldown routines)

M104 S0 T0 (temp zero)

M109 S0 T0 (platform off)

M106 (fan on)

G21

G92 Z0 (zero our z axis - hack b/c skeinforge mangles gcodes in end.txt)

G91

G0 X100 Y100 Z20 (

M18 (turn off steppers.)

G04 P120000

M107 (fan off)

(end of end.txt)