@OP: 45 or 46 is stock on the stock 12.12 (iirc, was it a 12.10? can't remember for sure rn, but anyway) mid 50s should be a good range to try. iirc I ended up around 60 with my 'stage 1' setup, and that was in spring/fall temps (pretty much all summer around here). I'm only around 70 now and the whole thing is wide-open (intake as big as I could get it, cut crank, bored and matched to mildly ported malossi 73cc, modified estoril).
@Jax: Those are two of the reasons I like mine, that and decent cdi, lights, and brakes. The subframe definitely needs strength and length for a good sized guy like me tho. I've been thinking about fabbing something bravo/grande length for a long time; for strength/weight it would be nice to use square tubing trellis or just plain square tubing, but it will probably have to be square tubing on trellis cut plate, as There's minimal room between the motor/hub and drive bits, the belt has to go somewhere.. If I ever get around to it lol, we'll see how long this reinforced one lasts.