I have been noticing more MacPros kept on top of desk rather than on the floor. Why is this. I think it's too big to go on a desk, even a big one. Is there something I don't know about. I guess the 'dust bunnies' may be a bit larger on the floor but it's also cooler. Getting to the back is just as much as a pain in both places.
Get some strong steel hooks and chains from Home Depot, and hang it from the ceiling. Why bother the floor and desk. Make it as a Mac Pro Air.