If you did want to go with the suspended rack idea in a high ceiling shop, one way to build it would be to use hanger rod to tie into the roof structure and then cut it to varying lengths according to your roof pitch to make it level at the desired height above the floor. Our shop roof is built out of bar trusses, so it's a cinch. Just slide a piece of hanger bar, or whatever is on hand, between two trusses and then screw the rod into that.

SSS