Well, maybe I am the exception to the rule, but I have used the plain old drug store medicinal alcohol to thin 30 minute epoxy for fuel proofing the firewalls on four different airplanes now, and I have not had a problem with it yet. It cures, sets up hard, and has NEVER made a rubbery mess yet. I wasnt aware I was supposed to be using only denatured stuff. It may not be the right stuff, but the drug store stuff will work though, I've got four fuel proofed firewalls to prove it.