I believe a few have tried using pci-e risers, sswilson amongst others. Don't know about the length, found a 2.5" here:
http://www.plinkusa.net/webR1PCI-E1-1R.htm
As for your board question, any size of a board can work with a NV580 - as long as it has a 16x pci-e slot. Cases and PSUs though, that's another story...