something to test...
 

http://www.redrc.net/2008/12/associa...-gears-for-bl/

72teeth spur for the B4

put slipper pads on it, correct the inner diameter to fit the prop shaft
test the slipper action, would it be better?

I don't have my racing pred anymore, it's up to you guys to try.

Been there, tried is many moons ago!! Yes it helps, but is an absolute nightmare to make everything fit together. Obviously not with those specific gears though. IF their centre thickness is thinner, then it would make it much easier to use them. I used std gears when i did it.