I am a private pilot and I just recently got my A&P mechanic license. I don't have a whole lot of experience, for now I pick up part-time aircraft work when I can get it. That said I still wouldn't want to try it. It may be possible though, ever heard of a Cri-Cri? Aerospaceweb.org | Ask Us - Cri-Cri Homebuilt Aircraft
I think that if I was going to build an airplane using these chinese engines I would want 4 of them. I know it sounds excessive, but with the right props it might just give you enough thrust.
The one thing you said that worries me is that you don't want to go more than 20 feet high as though that makes it less dangerous. That is a common misconception, actually higher is safer, it gives you more room to correct for mistakes or glide down in the event of an engine failure. Not criticizing you or anything, just please keep it in mind if you actually get your idea off the ground (pun intended).