Id go for a high revving (probably OS) .12 or the old favourite, the OS .18 cvrx I think it was, with lots of torque and reasonable revs. A .21 may well be a bit much for the belt drive and give you too many wear issues. I guess it depends on just how sympathetic you are with the throttle though. But personally, Id go for a decent .12, or wait for more opinions.
Oh - a lightened flywheel should help the throttle pick up quicker, thereby helping you spin the wheels easier, just watch for any idleing issues. You seem to know what youre doing, so I could well be stating the obvious there though.
ps - Hi to the gang.
