i get my CF from:
www.dragonplate.com
what most people are talking about i think is twisting the slider driveshafts, but i too have broken the connection to the stub axle twice with my lehner 5300 stampede.
the reason i do not use the CVD's is because they limit suspension travel.
the lehner basic 4200/5300 motors look really small, but they pack quite a punch. check out Candyman's website, he has a bunch of good videos with lehner motors. i think he used 2x lehner 4200's in a juggernaut 2, and it scooted along quickly.
Candyman's website
justin