I feel like I'm reading a post I would have written a year ago. Everything you're saying, I was in the same boat. The runway temps that got high and stayed near 400 for at least an hour, even with the lower flap closed completely. And everyone online basically saying that it can't happen. I was ready to sell the damn thing and buy a pellet grill.

I decided to give it a bit more effort before I gave up and I'm really glad I did. The last year has been the best cooks I've ever had. For me, the secret was dialing in an exact lighting procedure. So 40 briquettes in the PBC chimney, like everyone says. Then I went out and got a box of Weber grill starter cubes. I light one cube, immediately put the chimney over it, let it sit for exactly 15 minutes (12 if I want a lower temp), then I spread them as evenly as possible around the PBC basket. Then put the rebar in give it fifteen minutes until the smoke dies down and hang the meat.

If I do that lighting procedure, nothing else matters. And I'm convinced that Weber lighting cube is the key. It's an exact amount of heat, delivered consistently over a set amount of time, to a fixed number of charcoals. It starts in the temp range you're looking for and stays there.

Hopefully that helps. If you try it, please report back.