Here’s an SN95 rail for comparison to the fox above. I used an SN donor rail when I replaced my drivers side.
When you remove the top plate(left), there’s a welded subassembly (center) for the crush tubes. There is only two. That all drops down into the SN rail area (right). The center hole remains wide open to the interior cavisty, so moisture doesn’t affect the SN as much. They still rot out, but doesn’t seem as widespread as on the fox.
The fox has that same center hole but puts an additional crush tube over it and additional metal as shown above. The SN rail is just so much more simplified.
If I have any more pics I’ll post. I took a bunch when I repaired my rails a couple years ago.