Question: Which PCI-E Slots should I put both my GTX 980's in?
 
Explanation: I have an eVGA Z97 FTW motherboard. I have two eVGA GTX 980 FTWs to put in SLI. I have one back plate, and don't want to buy another. The manual (which is a joke) says this:
 

PCI-E x16/x8 Slot
 This board has a single PCI-E 16x slot. This is specifically for a video card, however you can place a different card there and use the Intel HD Graphics on the CPU. When installing a PCI-E Graphics Card, be sure the retention clip snaps and locks the card into place. If the card is not seated properly, it could cause a short across the pins. Secure the card’s metal bracket to the chassis back panel with the screw used to hold the blank cover
 PCI-E Lane Distribution:
 
PE1 – x16 (x8 if PE2 is used)
 
PE2 – x8 (x4 if PE3 is used)
 
PE3 – x4
 
PE4 – x1
 
PE5 – x1 (x16 Physical)

 
I feel like this means I'm supposed to use slots 1 and 2, and that that they both run x8. I would assume I would put the one with the back plate in slot one because of heat. However I would prefer to use 1 and 3, since the video cards don't have reference coolers.
 
Parts List:
/
CPU: (Purchased For $310.00)
CPU Cooler: (Purchased For $54.99)
Motherboard: (Purchased For $91.98)
Memory: (Purchased For $89.99)
Storage: (Purchased For $104.99)
Storage: (Purchased For $79.99)
Storage: (Purchased For $89.99)
Video Card: (2-Way SLI) (Purchased For $549.99)
Video Card: (2-Way SLI) (Purchased For $394.18)
Case: (Purchased For $79.99)
Power Supply: (Purchased For $129.99)
Wireless Network Adapter: (Purchased For $33.50)
Case Fan: (Purchased For $14.99)
Monitor: (Purchased For $450.29)
Keyboard: (Purchased For $69.78)
Mouse: (Purchased For $59.99)
Headphones: (Purchased For $31.95)
Other: LG Black 6X BD-ROM GGC-H20L (Purchased For $119.99)
Other: mod/smart Tailed 3mm LED w/ 2 Pin Mobo Header Connector – White (Purchased For $9.53)
Other: EVGA GTX 980 FTW Backplate (Purchased For $24.98)
Other: NZXT CB-LED20-WT 2-Metres Light Sensitivity Sleeved LED Kit (White) (Purchased For $15.79)
Other: Creative Sound Blaster X-Fi Titanium Fatal1ty Professional (Purchased For $129.99)
Total: $2936.86
Prices include shipping, taxes, and discounts when available Generated by PCPartPicker 2015-07-20 11:16 EDT-0400
 
Thanx in advance!

I can confirm that when putting a card in slot 1 and 3, slot 3 shows as 4x in the bios, and they do not SLI certify.
 
I'm an experienced system builder, but am quite surprised this is even a thing. Honestly, had I known, I would have bought something else. But I have it now. I'm seeing that the temps on the top card are quite high. Looks like I'm going to likely loose my overclock. I may even need to underclock closer to reference. 
 
It might be time for some /r/techsupportmacgyver with zip ties and a fan to straighten it out.

For the Z97 FTW, the cards will need to be in slots 1 and 2 in order to run both cards at 8x. This is according to part one of the manual, located here. If you were to install a card into slot 3, say a sound card or other PCI-E device, slot 2 would be reduced to 4x.