A friend has an old BW sled with an old 40hp and that runs a 12 x 15 or so. You might be able to go 17 pitch with a 50hp.
That little sled will be dangerous. Probably hit 45+ if it doesn't flip.
Check out
http://continuouswave.com/cgi-bin/Ul...i?action=intro for spirited BW discussion.
Good luck.