Question for those who have build multi GPU rigs using MCIO gen 5.0

Hi, Those smart ones, who have built multip GPU rigs with MCIO cables and adapters, which adapters and cable and cable lenghts have you used? I have 3 MCIO gen 5.0 components, and the problem is that they works only 8x 5.0 or 16x 4.0 speeds. I am not able to identify which component is the weakest link which causes errors on 16x 5.0 speeds. MCIO male to male cables are 80cm long: Adapter for the motherboard pcie slot is 16x gen 5.0 adapter which goes to the GPU is this: So with the above components, I can run gen 5.0 GPU only 8x speeds.