Excellent setup! Thanks for sharing. I'm looking to do something similar but am trying to think through the best option for configuring the power supply. My thoughts were to use an ATX power supply for the mobo and risers and use a server psu to power the cards. This would allow me to avoid connecting power supplies and take advantage of a cheap and highly efficient hp platinum server psu.
I'm curious if you've looked into this option. I'm trying to figure out the best size PSU to power the board and up to 13 risers.