RE: TT91 FS overprop'd?
I have set one TT .91 up for a guy at the field. The APC 13x8 worked really well, as did the APC 14x6. This engine did just under 10 grand with both.
Those are the first two I'd start with if I were you.
The TT .91 I worked with was a really sweet engine by the way - totally reliable from tank number one.