Rb5 with brushless... tight fit

[Colinevan]

Well im currnently fitting a spare 5.5 gtb into the rb5.

Its really tight and basically will squeeze in and virtually holds itself in without the need for tape. Question is, do you think this is bad as although its sturdy even when its taped in, it wont move around i.e its sustainable to shock. I could make a packer so that it sits slightly higher than the chassis ribs but that would increase c.o.g. what would you do?

Lastly has anyone any idea of gear ratios? or even better what pinion i should start off with for a 5.5 brushles?

Thanks

Col.