I have a 1/4 sopwith pup, with a Zenoah G-26. I use junky J-Zinger 18x6 propellers on it. It flies it just fine, but it won't do anything with a lot of vertical. I don't expect it to. That's the way WW I airplanes were. So I'm sort of wondering (in a polite way) if you're expecting performance that it's not really meant to have. Not trying to start a fight, I'm just wondering if you're wanting that model to act like a sport plane?