I tried on a h81 pro btc and it can't boot with more than 6gpu even if they are on 5 slots! So h81 have trouble with this, but the gigabyte z87x works like a charm, the only thing you need to know that you can put only 8 cards from one manufacturer AMD or NVidia.
I have a few H81 probtc, they can boot with 8GPU. 2X7990 + 4X7970 or 2X7990+4XR9 390.
Are you using usb risers or ribbon one and what are your settings in the bios?
For the pictures : it is an ugly wooden rig and i sold one of the 1070 yesterday! But if you want i will post the pictures these days!