I'm cooking for a graduation party in May. I'm guessing the pork butts will be about 8-9 lbs. How many can I fit on both racks of the 18.5 WSM? I've done 2 on top before so I'm guessing I can easily fit 4. I'm wondering if I can somehow squeeze in 5??? I'm guessing this much meat on the smoker will also increase cooking time is that correct? Thanks in advance!