I have been using an Enya SS30 to power my RingMaster and this 6.9Oz engine is quite powerful for its size.
I got it directly from my own store www.stunthobby.com but you guys can get it from Randy Smith in the US

It turns an APC 10.5x4.5 and using .015x62' lines I get laps around 4.8s.
It runs in a wet 2 and produces a lot of line tension.
2,5Oz of fuel of 5%-22% will be plenty for the pattern. I use a uniflow tank and it didn't need muffler pressure to get rock steady engine run.
The original muffler is light and works very well, only use a tongue muffler if you really need to balance weight.
I didn't have a chance yet to measure rpms, but as soon as I do, I'll post them here.
The engine comes with the regular click and spring needle, and that works ok, but one click will change quite a few RPMs. I will replace it with an Enya Pro NVA to give me a little more tuning precision.
Perhaps some one saw it flying at Brodaks Intermediary Profile, Classic and OTS. I was 3rd in OTS with it.
Martin