Tim,
If you want some more built in theft deterrence on that baby, just connect a lanyard (say some .027" stainless cable) to the safety valve. Connect the other end to the footing or foundation of your shop to keep it out of the way. If someone tries to wheel it away, it yanks the lanyard and the whole tank blows down. Very loud. Hard to run fast when you just crapped your pants.
Divot McSlow