I started with 40#s. Empty, the pit came up to 240* in an hour. Put the pig in. Struggled to hit 220*. As more cc was added the temp struggled to hit 200*, with it sliding down to 180*. The pig temp held (to a graft chart line on where it should be) to about 8 hours, then falling behind. At the 10th hour I pulled the plug on cc and went to wood.
The fire box (2 ft cube) was full of cc, sloped from the back to where it would been hard to get more in. The whole bed was lit with a blanket of 1" high flame over it. That bitch was hot, but wouldn't heat the cook chamber.
When I added 2 logs on top the temp went right up. Some guys have good results with cc baskets, probably because of air flow like you suggest.
I think I'll stick with wood and coal black pigs. Was that a hill billy song title?