Call Keith at BME and see if he will build you a BME 44. Last time I talked to him--they were in limited supply and being phased out of production. His website claims to have them in stock--but you'd better call him first. He may still have some around and he might custom build one for you if your nice when you talk to him.

You need LIGHT. You don't want your wing loading to go through the roof and ruin the way the plane flies. Any 50cc engine is going to be too heavy. That BME 44 is the lightest thing your going to get that will 3D the plane and yank it out of a hover without giving you a wing loading of 35oz.

Check into it. I know there are guys here who will disagree with me. It's not about what engine a guy favors. It's not about which is more reliable or not. They are ALL reliable if you just tune them right and treat them to good oil. 95% of problems with gas engines are end-user related. It's not the engine.

That BME 44 will be the lighest setup you can get. It will put out the power you need for your intended purpose. Check into it.