The following pictures show, from back of cab area to the tail of Clifford, where things are located on the present back of the truck. Any photo opened can be zoomed to read the tape measure to identify how far back from the forward edge of the middle Catwalk platform an item or area is located.
The forward edge of that catwalk was picked as an easy reference point because it lines up with the grab handles on the side fairings of Clifford and makes it the forward-most point that the side of the smart could be placed once loaded.
The white chalk marks indicate the 60” point which would be about where the smart side facing the rear (plus 1.1”) would come if lined up on the front edge of the catwalk. This is just as an easy reference to get perspective and measurements.
In the last photo, the middle chalk mark of the 3 is 60” rearward of the first chalk mark (back side of the smart). The two marks bracketing it are about the range of where the pin would come in this hitch.
Clearly, this hitch must be moved back. It is presently in the rear most lock position on this sliding platform. The whole platform can be moved farther back by unbolting it and then unbolting the support flanges under it and moving them rearward. I don’t think that it will be necessary to add any extension to the main frame rails to do this.
A lot more pictures and measurements of Clifford’s bed area are available on my Full TIming – Smart Car Deck Project gallery. The originals are 4k x 3k pixel photos so displaying the original form of a photo might be slow on a slow internet connection. Fortunately, Smugmug displays thumbnails and provides a number of alternate display formats by default so the choices are yours once you are there.