I've never used it, but...
The organic solvents used in some glues could deteriorate the mylar from the capsule. I wouldn't risk it, as you can also put a thin sheet of rubber into the shell.
I don't know what keeps Plastidip liquid. But I've experimented with a bitumen mixture that's used for roof repair in cars and it ate the tweeters on one occasion. I've never used it again, also because after months it still gave off an unpleasant odor. I've used bitumen sheet since and that's made for automotive use. It still reeks for weeks though. Especially in the air exhaust of the heater. So if there's a tube in the shell, I'd be double careful.
