Dave,
Thanks for replying to the question about the YS91. Would you please answer a couple of questions? I'd love to take advantage from your experience before spending the money.

1) Did the Tru-Turn nut and the washer from YS allow easy attachment of a spinner?
2) How did you find the performance compared to other 90 size engines?
3) Are the mounting lugs the same as on engines intended for fixed wing use?
4) What size props were you able to turn and at what RPM's?
5) How much did the entire package cost after you bought the drive washer and tru-Turn parts?
6) Would you do it again?