speedchaser does an under size sc pully that goes bloody well from all acounts. this is a fully re-manufactured unit and does not suffer from the "turbo" effects of the larger crank boost wheels ( it's smaller thus reduces rotational inertia rather than biger and increasing it ).
here's a link http://www.speedchaser.net/small_pulley.htm
also running the sc all the time, .... well I'd be buying a couple of spare engines and sc's to do that.