Crossfire Placement Question

Specs:
Win7 64 bit
Crossfire 6870s
MSI Z77 GD65
8GB Ram
i5 3570k


So for those who don't know, my motherboard model has 3 PC express 3.0 slots, and in my current crossfire setup, my 6870s are sitting right on top of each other in the first two main slots. Now, my problem is that one of cards ends up being about 10 degrees hotter than the other, jumping up to 85-90 degrees in intensive games like BF3. My question is whether I can buy a super long crossfire bridge and place one of the cards in the 3rd slot to lower the temperature.
So the pairing of the cards could either be:

1st slot and 3rd slot
or
2nd slot and 3rd slot.

the speeds of the slots goes as such:
1st= 16x, but 8x with card in 2nd slot installed. With 3 cards installed, first slot is 16x while 2nd and 3rd are each 8x.

Am I gonna have any compatibility or performance issues doing this kind of placement setup? Thanks very much for your help.