I think you will be happy with the performance of the 1.20 in the SB. It's a good combo IMHO. Prop clearance may be the only issue. Keep in mind however the savings in fuel cost is substantial with gas. The 20cc gas will burn half as much at $2.50 a gallon as the 1.20 at $15 a gallon. It's something to think about if you fly a lot.
David