That was the challenge.
The rails help keep the tires on the tracks and strengthen the planks against deflection. The bed planks are located on pins and the front ends toggle under the bump stops to prevent flip-up.
The ramps slide into place with gate pins.
Just makes it.
Tied down to the front against the bump stops, the Z force just fits and the ramp planks disconnect and store between the bed planks. The bed planks reduce the proportion of machine weight taken by the tailgate and its straps, to a fraction of what it would otherwise be.
Tried both and loading forward seems more practical than backing up the ramps, which would be almost impossible without the backup camera.
Loading backwards shifts only 15 Kg from the rear truck axle to the front one! I thought with all the motor stuff toward the rear of the SXS it would be a bigger difference. A local commercial scale allowed me opportunity to test this.
It's under the GAWR for a 2500.
I intend to hole drill all four side rails with the ramps loaded, at the spot where truck tie down attachment points are, so I can cable lock the ramp system for storage and to help keep them from wandering off.