Just a quick note - I'm an airline pilot. I do believe airlines will only reimburse you for $500 for lost luggage, although you may be able to purchase additional insurance. You could always Fed-Ex it to yourself if you can't carry it on. Security has to ask about stuff like that, when you explain what it is, I wouldn't expect any issues. A solid metal regulator that weighs maybe a pound or more and could easily pummel someone to death on an aircraft - no problem! Just don't bring your nose-hair clippers. COMMON SENSE PREVAILS AGAIN!
I've never tried it, but you could ask a TSA agent to lock your case AFTER they have inspected it, just like they would a weapon case. They HAVE to x-ray it (don't put your film in checked baggage!). The answer may be a "TSA-Inspected" special tape put on your bag, and/or a TSA "zip tie" on the bag. If that is broken and something stolen, the airline would have some serious explaining to do and would have a tough time denying responsibility in small claims court.
Don't know if that helps any, but in my job, that's what I see happening. Don't check it!
EDIT: Just saw another airline pilot posted right before me. What he said. ;-)