I think a 12-7 APC prop may be a bit too much for the OS 61. I have one, its a smooth runner but puts out disappointing power. I would try a 12-6. Or better yet if you want to try a better engine in that range go for the Tower HObbies 75 and then the APC 12-7 would work great! The smaller TH engines are more finicky to adjust but the TH 75 is a terrific value. As far as the looks of a prop on a warbird, once you start the engine and taxi out 5 feet who sees the prop any way?!? To me its what works well that counts. [8D]