I have a H9 funtana with this engine and so far ive been a little discouraged with the performance. I got more pullout with my saito 100 then this. I have tried an 18/6 menz and a 17/6--the 18/6 was better but still not as good as the Saito 100 with a 15/6 apc. Is an APC prop the answer. Im obviously looking for a lot of pull out power for 3D. Anyone else try different props with better results?

Try a mezjlik 18x6, Xoar 17x7...So far I haven't heard of a better prop than the mez on a 26cc gasser.

It ain't the prop - the Funtana 90 on that engine with a 18x6 runs in 9000 10000 range -on a stock pipe setup from Horizon.
The in cowl mufflers run OK but power is waaaaaaaay off compared to the stock factory pipe -or the Skorepa pipe pictured here
the this thing is ballistic compared to the glow engined setups -we let others using YS setups fly it - they were in agreement.
I put in a lot of time with both pipes- power was same but th carbon fiber setup is much more quiet. Also I flew the other 26 I had on stock Evolution Pitts muffler - good power and would hovr and recover this Velox. but no comparison