If you read the updates on the first page, I was the user who reported the substantial difference in SLI performance when using the lower slot for SLI on the P7N Diamond.

I wanted to let others users know that I have since had reason to move the card to the lower slot again and found this time that I only lost 2000 pts in 3DMark06 (compared to my previous 4000 pt loss).

Interestingly, I have also dropped from 2Gb of RAM to 1Gb, suggesting that my real performance drop due to slot change is most likely to be in line with others - around 700 pts or so. I will confirm when I get my other stick of RAM back.