Set up for my second WSM smoke yesterday morning. Lit her up Minion style with a half chimney of RO lump dumped into the depression in the charcoal ring. Twenty minutes later, dead stable at 280, clear blue wispy smoke, everything is lovely. Put on ribs on bottom rack and sirloin roast on top. Problem occurred two hours in when I pulled ribs to foil and rotate to top rack while I put spatchcocked chicken and thighs on bottom. I left the lid off for about ten minutes while I reshuffled things and when I came back,flames were shooting above the (empty) foiled water pan. Put everything back on and replaced lid. Temp shot up to 400. Closed bottom vent and removed door until temp went back down to 275. Replaced dorr, temp went back to 350. End result, I fought with temp spikes for two more hours, ribs got somewhat overcooked (bones fell out, but meat was still excellent), sirloin overran to 160 IT but after foiling and resting in cooler still tender. Spatchcocked bird was almost perfect, thighs a bit overcooked. I guess the moral is to put the bloody lid back on when you are rearranging stuff so the air doesn't get crazy. WSM is very forgiving.