This is a great question. But from what I've learned mixing is a great idea. The problem is lump burns fast and hot where as KBB burn consistant and slow. So a goo mix will give you a nice cook. The only issue I have is the little pieces of lump, if I could get my grate to the point where the piece would not fall through I would probably use all lump. As for now i use a couple of rows of KBB on the bottom, lump and wood in the middle and KBB to start the party off. BTW I am using a 22.5 WSM. What do you guys think ?