Good point. I've seen that the head space differes a bit from brewer to brewer. I just think the head space created by volume dissplacement of the wand is fine,just right for each bottle type/size. And I have a few different styles of bottles,even though they're all 11.2 & 12oz. Or they're 12oz'rs filled to only 11.2oz? The wand knows the right level!
Everything works if ya let it-Roady(meatloaf)