Mine look like this (sorry no closeup photos, unless someone took some at JV that show the rails).
Some primitave ASCII art ( a lost talent )
Air Side = body side & door above
...........|
...........| rocker attachment below door
........../
......../ Formed 14 gage sheetmetal rocker guard
....../
..../
.../__________________
...|---------------|.....|
...|_____________|.....| pinch weld seam attachment
--------\
---------\ 1X3" 0.120 wall slider tube
The ground clearance is the same elevation as the pinch weld seam. The stick out 1.5 inches outside of the door sill to allow you to lever around rocks without door rash. The formed sheetmetal is asymetric with a left and right side to match the XJ body pinch weld. The guards are screwed below the door the full length of the rocker, and at the pinch weld seam.
I fabricated material to build three sets as prototypes and have not destroyed the first set (or the XJ, yet). They will support the XJ on a high liftjack and all the other "tests."
Maybe someone can improve on the concept?
A (sorry dial up guys) large pic, thanks to Michael Rollins for his JV photos.