1:
I'd like to build an autogyro. It's definitely on my list of "someday" projects.
2:
A control line autogyro would be even more interesting, although I think I'll wimp out the first time and do RC, if I get to it at all (I want to retire tomorrow, with the income I have today, and live another 100 years -- too bad it ain't gonna happen!)
3:
An autogyro without collective pitch control is a positive-g only craft. In fact, the classic sort of crash with a Bensen style autogyro involves inadvertently tipping the rotors forward enough that their negative pitch slows them down instead of speeding them up, at which point the aircraft falls out of the sky.
3A:
So it may be physically possible to build an autogyro that'll do negative g's, but it'd take some pretty fancy doing.
3B:
Does anyone make a control line heli? Three lines, with collective as well as cyclic pitch?