This is a pic of the front side rail being to long for the front rail to slide back for cover adjustment.
This is the tailgate end of the side rail, I used these ends to put on the front end of the side rails.
This is a pic of the tailgate end on the front end of the side rail.
Now...
I have been in contact with Truxedo. They are sending me the ends that are all but flush with the end of the side rails. Part number 1118248. That will allow the front bar to slide back enough to loosen the cover. With the longer ends the front rail edges stick out to far to slide back at all.
I have just installed a pro x15 o my maverick. I have the same issue as you, it is very tight . The ends on the front of my rails are longer the same as yours. I couldn't get the 3/8th" between the front of the bed and the side rail. I am going to contact Truxedo about the issue. If you look at...