I've seen the coolest bike set-up here by "Elliot" I think - he has a black 914 with 17" Revolution wheels. Basically built an adapter to mount a qucik release fork mount, like one would use on a pick-up or on top of a roof rack bar, onto a custom "L" shaped adaptor, then the adaptor bolts into the 3 holes in the under side of the targa bar that were put there by Porsche for the optional 914 ski rack mount. The front fork is held on the mount right near the edge of the targa bar, behind the driver or passenger headrest area, and the back wheel then rests on the back edge of the trunk (with some padding if desired).
Technically this set-up is custom and not really even a bike-rack. It is sooo small and inconspicous you could leave it on at all times if you used it 1-2 week.
I want a set of these adaptors and have $$$ but no machine shop! Somebody want to crank out a dozen for a group buy? dlee???