I went ahead and drilled out a hole with stepped drill bit--with a little olive oil rubbed all over it, thanks for the tip. It's at 7/8 now and I'll probably make it 1 1/8" later on. But for now I'll just start with 7/8 holes. I need to add one more slider vent towards the front, and then a capped nipple in the rear.
Mini WSM (Smokey Joe Gold), Weber OTG 22.5, GMG Davy Crockett, Hasty-Bake Suburban (Late 1970's), Bayou Classic 60K BTU Propane Burner, PGS K40, Smokey Joe Silver (for fish).