Hi guys, so i recently got a couple extra GPUs and some risers (otherwise they don't fit in my system, aftermarket coolers). I'm experiencing nothing but trouble. Please help!

System:
i7-3770k
Maximus V Extreme
2x Sapphire Tri-x 290x
2x VTX3D 290x w/GELID Icy Vision coolers & VRM sink mod
8GB Corsair Dominator GT 2133

Power:
EVGA G2 1300w

2x PCIe 16x 30cm powered risers (for the Icy cooled cards, they take up 2.5 expansion slots)

I'm having trouble with risers when over 2 cards are used. Managed to get the pc detecting a riser attached card today by wrapping the riser in tinfoil and then wrapping in tape. However, running a stress test just freezes the computer.