My advise for storing the rig would be to have the bottle on your back (depending on the bottle you could either put it in a backpack of some sort, or the CountyComm Hydrant pouch. If you go with a dual reg setup, a frag pouch should hold the secondary reg.
lol... Because my BAR doesn't empty its mags completely (1 round is always left) When I went to cock it to test trigger pull I think I turned it sideways, that bb fell into the chamber. Let's just say I'm very happy I was aiming at carpet. Rule 1 always saves you if you fail on rules 2 or 3.