[MetalMan]

Aluminum may be a better material for the brake spacer because it is thermally conductive - as is the motor mount. CF won't transfer any heat, so your motor might run a bit warmer than with an aluminum brake spacer.

Here is something else to consider: you could use a smaller servo for the rear brake only to save weight, and then mix in motor brakes since the motor brake tends to get transferred to the front anyways (this is what causes these conversions to push with motor brakes only). With this setup you can tune the braking from your radio without messing with any linkages. It's just a thought, and this is the setup I am using on my 1/8 buggy.