No problem, in reality anything you line with even 1/2" of drywall would be fine. I took a propane torch to a scrap piece of the drywall after I built that. The paper had a hole burned in it, but it self-extinguished (treated to do so, no doubt) and I heated the exposed gypsum until there was a noticeable orange glow from the gypsum itself, which stuck around for a few moments after I removed the torch. The backside was only slightly hotter then I'd like to hold my hand against (120-130F, estimated with calibrated fingertip)
I then realized that my box was severely overbuilt :whistle: