Can you explaion the "Sure you're not going to run 1080ti's" statement? why not? I have 1080tis in all my rigs right now, and was planning to put 8 in this one. OEMs regularly stack blower cards right next to each other and they work fine..thats what I was planning here?
This board going to have massive problems with hot cards! Dont forget, the hoter your gpu is the slower it works. So single Sapphiere RX 580 Nitro+ can do 32.5 Mhs with ETH at 70°C it becomes more memory errors and need to be restart or it hangs in windows same problem will be with linux. What happens if one of the this china capacitors are dead? You need to send it back and your miner stops making moneys... =( Sorry Octominer but its fail!
I prefer this mainboards
http://www.biostar.com.tw/app/en/mb/introduction.php?S_ID=886 and simple 008C Risers which I can change if they are dead it also cost less even with CPU and have 2-3 Years warranty.
That's nice you like those boards and risers. Calling the Octominer product a fail is a bit harsh, sure they might not work for your needs but each approach has pros and cons.
I have two riserless rigs (not Octominers but basically the same form factor). I'd recommend nvidia cards with them as they run cooler. Sure you're not going to run 1080ti's (ok hybrids would be awesome but that's going to cost a shitload) but cooling 1060s is no problem with 4 fans extracting heat and 1070s are OK with intake fans and smart heat management around the rigs. I don't miss risers at all on them.
If you are building a bunch of rigs riserless are less hassle too plug in the cards, ram + ssd, connect fans and you're away.