Nice concept and I have two comments:
1. Can you turn the pipe clamps around so the handles are inboard of the cross bar instead of to the outside? That would greatly reduce your head-bumping liability. It looks like the adjusting screw handles pivot enough to allow you to turn them with out hitting the pipe.
2. Try to find a couple of super-cheap seatposts to dedicate to the stand. Steel MTB posts would be ideal as you could clamp them as tight as you want and not worry about marring your good ones.