Tommy
Interestingly enough, I too got a chance to run my 4 blade props this past Saturday.
I was turning a 14X11 and felt it was too much. So I went back to the 15X10 and actually felt like it almost wasn't enough prop. I do have a 15X11 and I think I like it better than the 15X10.
I plan to cut the 4 blade prop down some and try it again.
BTW Just for those of a curious mindset

On Saturday Nat tried an 18X8W cut down to 15 inches on his OS91FX. It pulled like gang busters but was noisy. Bet it'll get better after he whittles on it somemore
Eddie