PCI E slots of Asus P6T

Hi,
I'm planning on getting the Asus P6T vanilla version for my i7 920 system.
I was wondering how the expansion slots work out.

I can tell that there's total 3 PCI Express 2.0 slots..
and the description says it works as 16x/16x/4x in Tri-SLI configuration.
However, what happens if I put one card at the top slot, and another at the bottom
instead of two adjacent at the top?

so it's like

=======================
GFX CARD |
=======================

====================== <- PCI Express slot

===================

=======================
GFX CARD |
=======================

Will it run at 16x/4x, or 16x/16x?
I want to do this so that there's space between my two GTX 275's, so there's adequate airflow.
I'm using a mid tower (storm scout) and I dont want the two cards to be stuck together to worsen the flow,
since two high end cards in a mid tower is already a heat-seeking problem.
thanks

maybe you can put your gfx card on the bottom slot and see what the bandwidth is?
cause if it goes 16x when yhou put it on the bottom, that means the rates aren't fixed right?