The Xoar 18x10 was one of the props I tested. I didn't tach it, but I did one flight with it and it was clear that it was not adequate for a 10.5-lb pattern plane, and almost assuredly not for a 12-lb IMAC model. I haven't actually used it on an IMAC-type model, but I've seen enough to bet the farm that it wouldn't work out. I tached a couple of the APC 18x10's and they consistently turned about 8200 rpm. All the flavors of APC 18x10 that I tried (pattern, sport, old-style pattern) pulled the plane pretty well but were noisy and just didn't have quite enough pitch speed for pattern.

This engine likes the revs! Find a prop that permits over 9000 rpm and you will be happy. Even for pattern, my engine is quite happy with the 15.5x12W turning 9200 rpm.

This is why I think you might end up with an 18x8 (at most! - maybe even a 17x8!!) for IMAC precision, or whatever prop Todd was using in the recent video that produced 22 lbs of thrust![sm=thumbup.gif][sm=thumbup.gif]