Ya know I didn't really think there would be that much difference in performance between 10% & 15% fuels when being used in little .46 size sport engines. Just recently I realized how wrong I was. I always buy 15%, usually Wildcat because that is the best priced around here & 30% Cool Power for the Saito. A friend that flies helis gave me a full gallon of 10% that he wasn't going to use, so I said sure I'll burn it, won't even notice it with my little engines. Lol, As soon as I started burning it I noticed that all my OS .46's & my Tower .46 seemed like they needed to be re-tuned or something. It felt like I lost the top 20% of my power-band. Now these engines never need tuning, they run great all the time. I finally remembered I was running that 10% he gave me so I ran a tank of 15% just to see & sure enough all my power came back! So apparently even as little as a 5% increase in Nitro makes a significant difference in power. We get real good vertical performance on my WM Ultimate 40 with an OS .46FXI swinging an APC 11X6 with 15% fuel.

I'll bet you pick up performance just going to 15% fuel. Then if you still need more vertical you could try that APC 12X4 prop.

I don't think the price difference for the 15% is but a buck or two at the very most. I have a lot of friends with the TT .46 PRO engine & they all run great on 15%. They run so good I've come to like them better than my OS engines. I think they give more bang for your buck!