I fly a lot of wildhare r/c's planes and have had good luck with them. Great planes makes a aeromaster bipe with a huge wing area on it there are a lot of 50cc planes out there as you said putting a 26 size gas on a 120 size plane has been done with good results a 50 cc on a small air frame to me sounds like a real disaster waitin to happen. Most of the planes on these videos have a 50cc the cap is a 58 all are rated for the engine size and the power is obvious. http://www.rivervalleyflyers.com/Vid/index.html