Simply modified the xml flie ReplicaterG uses when uploading a new firmware to the printer:

Inside the ReplicatorG folder you will find it inside the "machines" folder - replicator-sailfish.xml if remember right.

you can modifiy this line for example: (I removed the xml tags, forum software usually deletes it anyways)
axis id="x" length="227" maxfeedrate="18000" homingfeedrate="2500" stepspermm="94.139704" endstops="max" Pulley dia: 10.82mm / 1/8 step = 1/(10.82 * pi / 1600)
axis id="y" length="148" maxfeedrate="18000" homingfeedrate="2500" stepspermm="94.139704" endstops="max"