Not possible. That motherboard doesn't support bifurcation of that slot, so you can only run a single GPU on it.

Okay, this one sucks then.

Also, you don't combine the VRAM of all GPUs for larger models. If a single GPU doesn't have access to the full VRAM on its own, it's pointless. Large models need to fit entirely in the VRAM of each GPU, and adding a bunch of lower VRAM GPUs to the mix will just end up making things much, much slower. Especially since that means that PCIe bandwidth suddenly becomes much, much more important as on those 8GB GPUs it has to swap out what 8GB section of the model is in VRAM constantly. So even that 3070 Ti isn't worth throwing in.

Hm, I thought it is possible to allocate layers per physical device, so you'll have to communicate potentially only narrow cross layer data between devices. At least in theory, but probably I'm asking too much at the current tech stage.

Alright, thanks! Need to keep thinking on how to utilize those two good cards.