What else to add?

I have an X570 extreme board, running a 5950x processor and a 128gb memory. 

I have an RTX 3090 in the first PCIE slot and the third slot has a LSI card.

I was keeping the middle PCIE slot for an additional graphics card. However, its too problematic with the vertical GPU riser.

I looked at putting in a Maple Ridge Thunderbolt 4 card, but it looks like my motherboard may not be compatible. The idea was to have an eGPU graphics card and additional devices connected to it for a virtual machine. Does anybody have something like this?

One other thought was to run a 60cm Linkup PCIE 4 cable from the PCIE slot, through the back of the PCI slots and into a customised cage holding the second graphics card. This would need a separate PSU to provide power to the graphics card and cage fans. I already have a separate PSU. I could mount the separate PSU under my desk out of site.

It would also allow me to swap PCIE components easier, If I want to remove the graphics card. It would be a pain to run an additional 'hotplug' from the PSU of the server to the additional PSU, which means I would need to manually turn it on / off. Although I could do this if need be.

You can see pics of the existing build here:

https://forums.unraid.net/topic/120538-fractal-design-meshify-2-xl-and-define-7-xl-as-server/

You can see its pretty full, so I can install a second aircooled graphics card, behind the vertical RTX 3090, however the PCI cables may not fit because of the RTX 3090. I tried ordering 90 degree adapters a while ago but they were the wrong configuration. Putting the second card outside of the case makes sense, however if I do an EGPU, I will need to fill the middle slot with a thunderbolt card, or do the dirty external card solution, which at least plugs directly into the PCIE slot.

Any thoughts?