I think you want to talk to Bobby Wilson at Cactus Aviation. Real nice folks and maybe they can download a manual for this engine.
I use a 26-10 on mine flying a 33% very heavy kit built Lanier Extra and no, I don't have hover ability but it otherwise flies it great. Should have had a 100 in it but they hadn't come out with one at that time.
I've noticed lately that everyone seems to be going back to 40 to 1 oil ratio lately.
And, using Lawn Boy petroleum oil. See what Bobby Wilson recommends but I have gone back to 40-1. I may be mistaken, but I recall Cactus recommends 50-1.

3dbob