RE: OS .91 FX in a classic pattern?
I think the old .60 had an 11x6 on it. When I got the .91, I somehow managed to put the recommended 12x7 or 8 on it. But, I moved shortly thereafter, and haven't been able to play with prop sizes for a while. (I'm just now getting ready to play with it again.) My LHS has a Macs header for a .91 FX, and a 15CC pipe. The pipe looks like it might be the right size, but I really don't know. So keep the original diameter, but go up in pitch?