Does the bike wobble or does the pvc hold it tightly?
I can't speak for the OP, nor do I wish to steal his thunder, but I have also built a bike stand with a similar PVC latch. On the first attempt, the bike did wobble and would slide down on the seat post at the latch. I modified the latch by adding some rubber gasket material to it. It works well now... Here is writeup I did on the attempt if anyone is interested...
That looks like it might be a lally column(sp) which is a column with a screw jack, used to support sagging beams. In this app I guess it can be installed under any beam, or with a bit of plywood on top, it could be installed against a finished ceiling. Damned clever of the OP.
heh actually when i bought that base http://www.hauntershangout.com/graphics/projects/reaper/box2.jpg my original idea was to bolt it into a fence post or something wooden outside my house. After looking around i didn't really have a great area to do it so i rigged the clamps to the beam in the garage. A more elegant and simple solution is the just bolt that base to a tree, fence post, plywood or whatever and have the 12 inch pipe and clamp coming off of it. you can unscrew the pipe and clamp when your not using it and just the small base would remain.
ebrady, nice writeup! i think im going to steel your rubber gasket method. The foam works ok but your version looks like it will clamp nice at tight. Finding the right foam with an interior diameter of the seatpost and a exterior which fits snug in the pipe is tricky.