How many pcie extender have you been able to run on a single motherboard? I heard that for some only two slots works per pcie x4 slots, is there anyone running more than one of this extenders on a single mother?
check pcie lines on cpu side, and its safer buying other mobo and limit around 12gpus each of them, just in case crash happen only affected smaller number if you trying build bigger farm, yeah single rig you want maximazing gpus on single board, never try above 12 gpus on windows side, linux maybe helpfull on this.