[tatter06]

As it's a proxy entry and you're building for other people to race it and need to build in reliability I'd put an axle spacer between the bearing and crown gear to stop the gear moving.

...and don't forget the pinion 

Haha  it was just a rough test fit to make sure everything went together, there was a bit of rubbing between pod and chassis somewhere so need to get the files out. Noted on the spacers, I've never bothered with anything like that for club racing, I occasionally race nsr f1s and even got rid of the axle spacers to save a bit of weight. With being able to fettle it after every 3mins of running I've not had any problems but I think I will go all out with trimming the motor shaft flush and spacers inside and out side the pod to keep everything where it should be. 

One thing I found on the nsr F1 class is the alloy hubbed gears from slot.it (the only change allowed apart from wood guide) seem to run smoother and wear less than the brass ones, and I think they weigh a bit less too.