I have put the patch on the inside with a dab of aquaseal in the hole after. I've fixed bladders, a wet suit and a dry suit that way.
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I should have known without asking since the patches are not that great in certain stretch-requiring locations on jeans.Jeans patches typically have no stretch and the heat needed to iron them on (since they're designed for cotton) will probably not be so good for the nylon fabric around the patch, or the neoprene for that matter.
Bicycle patch glue is plain rubber cement with naphtha as the solvent. On a bicycle tube that's fine, but it is not a very strong adhesive. If you get a grip on the patch you can pull it off. Aquaseal is way stronger, although it stretches less. E6000 adhesive (the thin black version) probably also would be good. Neither one melts neoprene.
Thanks, Magnus. I wasn't thinking of the high-tech bicycle market, just of the plain black vulcanized rubber that all the mass-market bicycles are using.