I would have the same issue as I run the IVO IFA UL also. But knowing that others have flown hours and hours with the UL blades on a 912S Rotax, I don't think that will stop me from going to the big bore. And honestly, with more HP available, maybe I will just need a fixed pitch prop? In many regards that would be simpler. Av8r3400 has a huge 2 blade Prince on his Zipped up Model 4, and from what he is saying that's probably all a guy needs, because you get a better takeoff and climb, but yet have enough power to cruise efficiently.