So here is what I got working on the ASRock Z87 Killer

BIOS
PCI-E 1 (gen2)
PCI-E 2 (gen1)
PCI-E 3 (gen1)

PHYSICAL
PCI-E 1 (x1)   --> EMPTY
PCI-E 2 (x16) --> 750 TI (no riser)
PCI-E 3 (x1)   --> EMPTY (Blocked by PCI-e 2)
PCI-E 4 (x1)   --> 750 TI (1x riser, shorted)
PCI-E 5 (x16) --> 750 TI (16x riser)
PCI-E 6 (x1)   --> 750 TI (1x riser, shorted)
PCI-E 7 (x16) --> 750 TI (16x riser)

I have not been able to get PCI-E 2 (x16) to be recognized on a riser at all, either 1x or 16x
I have not been able to get PCI-E 5 or PCI-E 7 to be recognized with 1x risers.

I would love to get the 6th card up and running on this board.

Ideas?