Scott; How do you do it. I have 2 McCoy R/H 40's, and niether one will run reliably on 10% nitro. I have tried different props,and even adding head gaskets, and they just do not run right on 10% for me. They are both on profliles, and maybe that is the difference, but they always cut out after leveling off inverted after inside loops. I go back to 5% and they run fine. On my Magicians, I have been running 12-6 APC's cut down to 11", and the engines seem to love this prop. I run non uniflow, Thunderbolt R/C plugs, and Sig 25% all castor fuel. With this setup, they run a pretty much solid four stroke through the whole pattern until I get to the clover, where it rockets to the top of the circle after the second loop in a 2 stroke. They do make gobs of power with this setup. I have never tried running 4 pitch props, and maybe that would let the engine wind up a little more so that I could run 10% without it cutting out on me. There are times I would like to run 10% so that I would not have to take 2 jugs of fuel to contests as this is what I run in my Fox 59.