I have a friend who hangs out at the Mosquito factory. He went down there a few years ago to start building his helicopter, but has hung on to help write the construction manual and play around with the technology at the factory. If you need someone to talk to about that, let me know and I can PM his info to you.
I have another neighbor who built a turbine powered helicycle and flew it the place for a while, but decided that he wanted a plane he (and his wife) could actually go someplace in, so he's started on an airplane homebuilt.

We all take a good laugh at that old "back of the Popular Mech" weight shift goofball design. It's not clear that any of those actually "flew."

As Steve points out, the powerplant is daunting. Things are a little easier if you build it to light sport requirements rather than ultralight. The mosquito I think was a Canadian design (and a tripod gear). The guys who run the Mosquito factory in Florida now are fiberglass wizards and managed to get a body and real skids on the thing and make it a bit more practical. Still the choice of powerplants is key. As with the helicycle, some of the small turbines work. They've looked at a variety of two stroke and four stroke things (last I heard they were looking at a snowmobile engine that seemed to have good promise on the power:weight ratio). Even the regular N-numbered light helicopters have powerplant issues. The MINI-500 (other than goofy management problems and the flooding of their factory) really was killed by the fact that the pushing more horsepower out of the engine that it was really spec'd to do caused a lot of failures.