I've also just done the 3 gear mod essentially following the PetitRC setup. I used Durango gold 6x3x3mm and 6x3x2mm spacers for a total of 8mm and cut down the old spacer to flip it. I found it helps to leave the "bar" that connects the rest of the spacer (after the mickey mouse cut) and use it for the lower part of the motor plate. I'll try to post pics if I have a chance to take it apart...