I believe the WM is worth the extra dollars cause
of the fiberglass fuse, and parts. I had an O.S. .90
4-stroke in mine....it wasn't real fast, but it sure was
sweet. ( crashed it ) I recently got another one, they
were on B.O. for a time.

It'll be the next plane up for me, same motor. Inverted
four stroke is the only way to go. Don't hack that
beautiful cowling.

Dave.