Here is my setup:
I have a Rennsport V.1 WheelStand with hard mounted CSPs (non-destructive), a Scat ProCar Sportsman Seat mounted to a GranStand 80/20 seat base frame, and custom mounts for Fanatec Sequential and H-shifters made of 80/20.
Dual sequential shifter mount made of 80/20 hard mounted (non-destructive) to the Rennsport Wheel Stand.
The shifter mounts sit a little higher than they do on Fanatec's single shift plate included with the Rennsport WS.
I only use them for the Fanatec sequential shifter, I can easily change it out from left to right.
There is a PS/2 Female/Female adapter (visible in bottom center of above pic) attached to the 80/20 shift mount with two standard Fanatec PS/2 shifter cables.
I use it when shifting between left and right sequential shifters so I do not have to unplug the shifter cable from the right side shifter port of the Fanatec Wheel when using the left side sequential shifter.
Fanatec H-shifter attached to X-CPO adapter and mounted on 80/20 support that can be attached to either side of seat frame by adjusting only two screws. X-CPO adapter is mounted to 80/20 using 6" wide aluminum plate.
Both sequential and H-shifters mounted to right side.
Both sequential and H-shifters mounted to left side
I also have a long (1M) PS/2 cable that runs from the Fanatec Wheel's left side shifter port and down the wheel stand to the H-shifter.
Since Fanatec wheels only support one shifter connection at a time, I just have to unplug the cable from the Fanatec Wheel's right side shifter port I use for the sequential shifter when I switch to H-shifter, no fuss anymore.
I over-built the H-shifter mount on purpose to minimize flex because H-shifter movement is a lot more violent than sequential shifters.
I am in the process of designing an 80/20 rig to replace the Rennsport WS, so I built both the sequential and H-shifter mounts so that I can use them on the new rig as well as adapt them to other shifters.