One option that you might want to consider is a Rotax 670. It puts out about 92hp and drinks about the same as the 582. Weight gain is about 10 lbs. The 670 performs much better than the 582 by far. Not to mention you use your existing motor mount and cooling system as well as instruments. Rotax Rick advertises all over Barnstormers.com
There's a 670 install thread you might like to see.
http://www.teamkitfox.com/Forums/showthread.php?t=5500