My Shadow came with the scope rail. After a dozen or so shots, the stop was bucking up against the plastic end cap. The factory had the set screw slightly behind the shallow hole in the rail, so it rode out. Haven't had any problem with mine once it was reset, but I haven't shot it that much. I guess you could just tap a new hole in the rail if you wanted to move the stop forward/backwards. Don't know what the rail, itself, is made of. Looks like aluminum. If so, that could possibly deform over time, elongating the stop hole. The aftermarket mounts are no doubt superior.
What, me worry???