Ron made a modification that permits adjusting a sling seat to have variable height.  Neat and simple!

These photos show a shelf with 3 brackets. A round bar [wood or alum.] is places in any one of the circular tube anchors. [One for the Pilot and on for the Passenger.] the back position raises the sling the front lowers the sling.

the other bar is placed in aluminum brackets bolted to the main spar.

The sling material will have reinforced foam sawn to it with seat cover. The pilot foam padding has more buildup in the back, the passenger less buildup. Removing the bars will allow for seat removal. The shelf will have to have stiff reinforcing bridging the left and right side because it holds the weight of the occupants. [ My bulkhead helps with the support and acts as a roll over support, but that's another story].

Disregard the composite bulkhead in the rear and the composite wheel well in the front photo.