Here is some info on doing multi GPU (8+) setups. It has some great insight into what all is needed. gstoner on the link is a Senior Director at AMD and is full of knowledge about this type of set up.
Nice link Keith, looks like AMD has a working MB with 16 S9150 made by Cirascale. But damn, those GPUs seem too close.
Hi Hawkfish
I see that your USB riser on amazon are sold out. Will you be geting any more? I hope that shiping to Europe is not a problem. I heard you guys talk about risers, that have a power converstion from 12V to 5V so that it prevents burning cables? Are yours with the conversion? How can we spot risers that have that, could you point them out on Amazon for me please. I will be building a few rigs in the future and would realy like some advice about risers, so i can get some quality ones, as i don't know how to spot the good ones Example: https://www.amazon.de/PCI-E-Powered-3-0-Verl%C3%A4ngerung-Kabel-GPU-Extender/dp/B01N3UVJHM/ref=sr_1_6?ie=UTF8&qid=1490771302&sr=8-6&keywords=USB+riser