I assume he's using the ST G90? If so, he'll have a good time. It should have plenty of power for basic 3D, should be able to hover just fine. Those .90's are actually really good engines as long as they get broken in properly. I've found them to be just as powerful as some of the more expensive brands and if tuned correctly just as reliable. They also use about the same footprint as a .60 and weigh about as much as a .60 as well. The only time I ever had problems with my G90 was when I tried using a Pitts style muffler. I think it was because the muffler had two exhaust tubes and did not create enough tank pressure. If you run into that problem, try pinching off one of the tubes to create more back pressure.

-Pat