WeEEEEEllllllllll......I kind of fudged the thrust line for the larger engine, so it is extremely possible for me to get a 13 inch prop on there. Right now I'm looking at taking a MAS 16X10 3 blade and cutting it down to 12-12.5 inches. It's now getting to where I need to prove a point. I was told that a small group of consults believe that if you cut the ends off of a "constant" pitch prop then you will lose efficiency because the actual thrust is at the tip of said prop. My belief is that if you had three numbers in the sizing of said prop (progressive pitch) then this would be true. Oh, and don't worry about the thrust line issue, I can always go back to the original mounting hole locations and work the smaller prop if it shows it is pulling to the canopy on the uplines and knife edges (if this thing can actually achieve a knife edge that it)