Gigabyte GA-Z77X-UP7 MB with 5 or more GPUs?

[digitsmith]

Gigabyte GA-Z77X-UP7 with 7x PCIE slots:

PCIEX16_1 (orange)
PCIEX16_2 (black)
PCIEX8_1  (orange)
PCIEX1_1  (black)
PCIEX16_3 (orange)
PCIEX1_2 (black)
PCIEX8_2 (orange)

When using PCIE riser cables I can only get aticonfig (Xubuntu 13.10) to detect the GPU on (orange) PCIEX16_1 slot.

Anyone mining with this motherboard using 5 or 6 GPUs?

It would really help if I can get a confirmation that I'm not fighting a losing battle - in which case I should rather be looking for a different motherboard?

[digitsmith]

Manual says:
The PCIEX16_2 (black) slot will become unavailable when an expansion slot is installed in the orange PCI Express x16 slot.

Moved 2nd GPU to PCIEX16_3 slot but still not working...