His design looks basically sound. No gyros are needed. The original Bell jetpack steered mostly by simple weightshift. He's got enough thrust to hover himself and fuel with one engine out, but during spoolup it could get exciting. He should be burning about 1 gallon/minute at a sea level hover. It might just work, if he's careful on his first test flights. The biggest difference between eccentric genius and nutcase is how much money you have.