In my opinion there is no such thing as too much power, just excess power!!!

Their is such a thing as too much weight.

With 3d flying it is vertical thrust and acceleration that saves me most of the time I screw up. That is why you should go with a saito 91. I know of a guy who has a YS 63 on a No Limit and it does fine. Some argue that the YS has almost the output of the Saito so it should be great!!

Make sure you build the firewall very well though, but don't add weight.