Henry Bibb wrote:
It sounds like you're a sophisticated cyclist. You might want to check out
the information at this site: http://www.sandsmachine.com/
They've got a widget that can be installed in the frame of your choice to
manufacture a folding bike, plus a list of about 90 frame makers who
will put together whatever kind of frame you'd like. (I suppose I should
say, the bike becomes "collapsible", in that it separates into 2 parts,
which then can be packed more compactly.)

I just called to ask about getting a set.
Because of liability, they will only sell to bicycle frame makers.
Bummer!
However, the September issue of KITPLANES shows how to do-it-yourself
with any bicycle.