Hardware Configuration for Passthrough Question

[DottedLine]

I originally made this post here: https://forum.proxmox.com/threads/gpu-passthrough-help.26989/
After searching the VFIO mail list I came across these two posts:

• https://www.redhat.com/archives/vfio-users/2016-April/msg00153.html
  
• https://www.redhat.com/archives/vfio-users/2016-January/msg00301.html

To solve the black screen / BSOD after installing the AMD video drivers they attach a ioh3420 pci-express root hub to the VM and then assign the video card to it.

Is this possible to do with proxmox and if so, how do I do it?