I am cooking up 3 Butts tomorrow. I have one 8 pounder and two 6 pounders. I have to work, so will be starting them at about 5 AM and my son will be taking them the rest of the way. I thought I would put the two 6 pounders on the same rack and the 8 pounder by itself. Will it make much of a difference, which goes on the top rack vs the bottom?