Hey Bob:
Of course you bought the right engines!

And Kris:
It just dawned on me, there's an easy way to test your theory about the rotary valve motor running out of breath at high rpm. Just do comparative tests with smaller props on the ground. If one engine is ported for high rpm power, it will show up with smaller props. However, someone could argue that the rotary valve motor was designed for a torquier power band to run larger props at low rpm where prop efficiency is higher.