Thanks Kris. I agree it's a heat problem, but there must be something mechanical that's putting it on the path to thermal meltdown. We couldn't keep it cool enough to prevent sagging after 6 minutes even without the cowl. I would think that any engine sticking out in the breeze at 60+ mph should stay cool enough. The owner will call Keith.

PS, what about prop load? These can handle a Menz-S 26x10.......? Right?