PC Cases that have space to install "3rd" gpu

Windows tends to have higher PCIe utilization than Linux for Folding@Home. Likely something to do with how it (mis)manages Contention for the bus. I found testing under Linux that only when you get up to a RTX2080Super do you start to see a degradation in performance using a x4 connection rather than a x8 or x16.

The x1 USB risers used for mining will tank your production in Folding for all but really low end GPUs especially under Windows so I don’t have any experience using them but they seem fraught with issues. My biggest concern with them is their use of SATA power connectors with under sized wire for the 75W PCIe power. I’ve seen many reports of people having them melt and one of our participants in a recent Folding contest had one of his rigs catch fire taking out itself and an adjacent system.

Ah, the Glaswegian accent. I remember visiting there the first time in ‘84 and going for Curry and Chips on Sauckihall? and ordering a pint of Guinness and a nip o’malt then noticing all the locals were drinking Budweiser and smoking Marlborough’s - very strange.

Tom M wrote:

I have experimented with riser kits and expansion cards extensively. I had trouble with reliability. I still like the concept but eventually switched to ribbon cables.

I have 2-4 expansion cards of the type you linked to. I also still have a single 1 to 8 expansion card. But my results with riser kits was "variable" and eventually something would stop working.

Odd, as the only problem I've had with GPUs is the power connectors.  They tarnish and drop some voltage causing a lot of  problems.  I replace the plugs often, and if the GPU side gets tarnished, I solder the power on directly.  I've never found the riser itself to cause a problem, even sharing one socket to 4 cards.