We saw the Boy Scouts use just a tinfoil frame to do this.
approx 30x30x30 but I brought some scrap aluminum home from work and this will cook a 15lb bird in approx 2hrs. We burnt 1 lb of charcoal to 1 lb of bird. a 23lb bird took 3hrs
We used a stainless steel rod with a 7 in. round plate to hold the bird and covered it with a cooking bag.
Hope to try a pork loin for pulled pork later this summer and maybe some baked beans