the .65 is entirely too, too much engine for the Eagle II even a good .45 /46 schnurle is plenty& many were/are flown on the FP / or LA engines.vibration is going to be a problem not to mention balance.the .65 flies the larger CG Cub with ease . with the larger motor even as 4 stroke fuel capacity will not be enough for longer flights. the FP /LA motors can be bought all day long for around $ 45 used. your problem will not be keeping it up-- it will be landing under power.