Seems to be. I just use Devcon, or hobby shop brand/Bob Smith Industries 15 or 30 minute epoxy for everything. It is completely fuel proof. I even use it to fuel proof the fuel bottle well in my flight box, and have left an inch or so of fuel standing in the well with no damage to the epoxy. Even Fox Missle Mist (I had an old can of it around that I use in the 049 jobbies) doesn't effect it.

I don't keep polyester surfacing resin on hand because I am horrible at fiberglass lay up and so I don't build from glass anymore, but when I did use it, it worked just fine for fuel proofing. Messy to deal with though.