So im new here. But after useing 5 diffrent grills propane charcoal and 3 diffrent smokers. Ive learned this question alot from all the forums. What i have learned thru trial and error is. It depends how the main chamber receives is heat. Top/bottom/middle... Were as my smaller charbroil smoker heats top down, and my grill is bottom up, practice on cheap meats to figure out how your cooking surface distribiutes the heat. It willl determine if your fatcap should be up or down. Let me know what you think or find...??