I'm also quite interested in it. There are many threads on this topic but no successful results yet.
You might need to install Linux and use some kind of virtualization to break the 8-gpu driver limit.
How well do you guys think this would work to add more GPUs to your machine? Would you be able to turn a 6 GPU machine into a 9 GPU? Are we still going to encounter issues with the motherboard seeing it? Very interesting concept. The most I've seen so far is 8 GPUs on one machine and that was tricky business.