While I'm no expert here, I do believe that the 'test" the ATF would apply is trying to twist the comp off the barrel. If it were properly silver-soldered (I've done some of that without any issues) you can't twist it off. If, however, you don't apply it properly you could twist it off the threads relatively easily with enough pressure. It's pretty subjective but I know that there is a regulation somewhere that states a ft/lbs number. Beat that and you'll be good. Still, it's a crap shoot with those guys.
I do have one question, however. if you pin a comp on your .45, would you still be able to disassemble the barrel from the slide? I don't have any experience with that type of setup.
Romeo