Found some info on line indicating EL34s can run at 480F. That doesn't sound right. Paper ignites at 451F under perfect conditions. I know we don't intend to glue anything to the tube glass, but I have had tube amps that ran perfectly for decades ... that were too hot to touch the back of the chassis and uncomfortable to try to hold on to the nameplate for more than a couple seconds. Amps can get very hot. I'm inclined to avoid using adhesives that are designed to melt, when I can get high temp silicone at Pep Boys easily.