speed wise case with 2x4 or 1x8 gpu's

[intertan]

I have noticed the more GPU's one add the slower the added gpu's work
ex gpu0 11153 mh/s
gpu1 11005 mh/s
gpu2 10985 mh/s

Now I just thought possibly aranging the cards to see if that changes.
while a case with 8gpu's makes more sence as far as looks I was after purly after over all speed.

btw I don't have 8 1080's just an example.