I did have to drill holes into the top of my rails to attach the covers rails The issue was a regular pickup bed has a under rail area for things to mount and hide without drilling, a step side does not have that as the under rail part is on the outside of the bed.
That IS an issue. Fortuneatly I found a bedrail clamp that I could modify to use the sideboard screws on my LRE and didn't have to drill the top rail. Not a fix for a regular utiline though.
