>> Asus P6t Mobo w/ 3rd GPU <<

I'm trying to run 2 GTX 260 in SLI mode for my primary monitor and use an 8800GT to run my second monitor. Unfortunately, the GTX 260s are so big that the one in the 2nd slot covers up the 3rd PCIe 2.0 slot (maximum 8x). Is there any way to work around this? Could I buy a thinner 8800gt, put that in the secondary slot and then run SLI from the primary slot and tertiary slot (primary slot is 16x max and tertiary is 8x max.. would that mean both would run at 8x? And would SLI even be possible?). OR, could I use a PCIe 2.0 extender or cable thingy? Are those feasible and performance worthy?
Thanks!