Alright, my board arrived a day early and I was able to swap it in to my rig.  It worked with all 8 1080 TI cards right off the bat, no problems.  I didn't do anything beyond the usual adjustments with the BIOS, so I think I know the problem.  My guess is that a switch to these m.2 adapters is all that you all need:  https://www.amazon.com/EXPLOMOS-NGFF-Adapter-Power-Cable/dp/B074Z5YKXJ/ref=sr_1_3?ie=UTF8&qid=1516773409&sr=8-3&keywords=explomos+m.2+adapter

On the MSI motherboard I referenced in my previous post, these m.2 adapters had some luck getting more cards recognized than people with different adapters, so I think these are the way to go.  The same adapters are available on the UK Amazon site, but under a different brand name.  I can't think of what they are called right now.

Good luck!