I've got my bj4 geared at 75 tooth spur, with a 16 tooth pinion, works perfect for the track i'm on,
one note too, the Mamba max set up is quite a bit cheaper than the Novak and LRP systems, its not ROAR legal thgoouh, but if your track doens't follow strict ROAR rules, the Mamba is an awsome set up, for a really good price, I had a sphere comp as well, and I prefer the Mamba max because its alot easier to program with the USB adapter, and for the price, performance wise I can't tell the difference between the two,