RE: SBV2 Pro and Novak 4.5 brushless
Little late for a reply...
I am using a Novak 4.5L in my SBV2 Pro. Works fine however, it does not seem to like FDR's above 10.5:1 since the greater ratios (10.5+) seems to cause excessive slipping in the diffs which lead to melting. This can be minimized by increasing speed slowly but since you will be on a tight track, punching quickly out of the corners will be to your benefit.
I have been using a 17t pinion and a 76t spur (FDR of 10.42:1), however, I am still slipping (and melting) more than I want and on a tight track, this would not be good. Since my buggy is up for a rebuild, I will be dropping down to a 70t spur while keeping the 17t pinion. This will give me a FDR of 9.6:1, which on a low traction surface should work fine for me.
I guess it will also greatly depend on your driving style, as well.