Man, you guys are probably getting really tired of my questions, but I just came up with another one. The boil size doesn't appear to impact OG or anything related to the content of the wort, but it does greatly impact IBU's. I can understand the former because it's just a matter of the amount of fermentables in the water, so the end result is the same whether you had a full boil or a small boil with top-off. But why does the hop utilization change with the boil size? I would assume that the bitterness and aroma would diffuse through the wort in the same manner as the fermentables, no?