I think that a tilt-wing or a tilt-rotor could be viable homebuilt projects, with a lot of ifs, not excluding somebody willing to design and built controllable pitch propellers with flapping and (probably) lead-lag hinges, either real ones or virtual ones (hingeless rotors have a soft-in-bending section in place of mechanical hinge). (Check out the VTOL Wheel for more fun homebuilding ideas; I rather like this one: ). Once one leaves out helicopters and compound helicopters, VTOL becomes hard, and for many of them, I'd want to have a zero-zero ejection seat, not just a ballistic parachute. Neither the tilt-wing nor tilt-rotor configuration is particularly easy, and both have disadvantages. I suspect (which means that I've not done a full-blown analysis) that the structural issues of a tilt-rotor are easier (for one thing, the wing doesn't need to move) but the aerodynamic ones of the tilt-wing are easier; it ends up being a trade study. Bell Helicopter had a lot of experience with tilt-rotors, so the V-22 was a tilt-rotor; had Hiller or LTV been major players, the JVX may have been a tilt-wing. Bluntly, I would not trust my life in any kind of tail-sitter, especially one powered by a piston engine. Give me a robust, well-proven gas turbine engine any day!