Currently, I have it closed, but assuming I go to 4 cards, I plan to leave it open...I didn't know about pci-e risers...I'll definitely look that up. This rig won't have water cooling, but I hope to add another rig expressly for mining this spring or summer. For now, I'm looking to make this a 4-card system. On my son's 1080, I run nemosminer...that's what I'd plan to run on slots 2 and 4 if I add 1080 vs 1080ti.
Thanks!
You can set the gpu groups in mining software. At least it's true for Nemos-miner and Megaminer, I haven't tried Sniffodgminer recently.
There is really no way to dissipate ~1 kW heat from 4 1080ti cards in such close space. And I don't think there exist any single or 1.5 slot 1080 cards unless you buy an aftermarket fullcover water cooling.
Just use pci-e risers and build/buy a frame for your rig.