I put the Lava Lok on the top and bottom of my 340 lid and it worked well but leaked out sides. Put it on the sides and like padlin it leaks out the bottom now.
Stu n, I've had mine up to 500* with no problem with the glue. Yours must get well over 500*. Maybe you should be sure the surface is really clean before applying the Lava Lok.
I put a little weight on the lid and it seals the bottom from leaking. I also offset a piece of lava lock on be top and bottom since the gap is a little more than 1/8". 1 piece on lid, 1 piece on drum.