I've done 8 butts on both my 22.5"wsm and 18.5"wsm before. You should have no problem with 6 on a 22.5"wsm. My advice would be to get the wsm good and hot before you add the meat, say 300°. Then add the butts and let it ride with all vents open, no water in the pan, and shoot for around 275°. I...