i have never cooked two butts before but i have a 6.5 and 7.5 lb butts i need to start on tomm night for work on friday. I didn't know if i should add the two together and figure 1.5 hrs which would be like 21 hours or figure the 1.5 hr rule for them idividually which would be like 10-12 hrs. Basically i need it to be done at 9 am so it can get wrapped and put in the cooler till 12 for lunch. What do ya figure?