NX 22-8 or NX 21-8 should do the job. I flew a Fox 3.2 (same cylinder as a Brison 3.2) with those 2 props on a GP 1/3 scale Pitts for a time. It wasn't unlimited, but it was plenty powerful enough to out of trouble.

(or INTO trouble in my case [sm=lol.gif])

It's been a few years, so I'm pulling these numbers from memory. It turned both props over 7000. I think the 22-8 was about 7100__7200RPM and the 21-8 was around 7600RPM. I liked the 21-8 prop and the higher RPMs. It just felt like it flew that big ole bipe better when it was spinning more RPM's. The 22-8 flew it okay, but the engine felt sluggish on uplines.

Consider I'm flying at almost 6000', so that might have a little to do with me liking the smaller prop and more RPM's.