Re: RG1XXV high e string moves progressively towards edge of fretboard up the neck
Headstock toward the bass side. 100 grit on the paper, cut to a strip just a little wider than the pocket, fold it a few times to give it stiffness, keep the edge flush against the floor of the pocket, and keep the pressure even. You want to sand more off the end of the side then the middle so you have to sand a little on the end, progressively sanding longer and longer strokes so you're sanding an angle into the pocket. Be careful not to roll the end of the pocket, keep everything straight and square and put the neck back in the pocket to check how straight the edge and the progress.
Do it with the trem pulled out, strings still on, so you can put the neck on, drop the trem back on, and check how far you've brought the strings over. The closer you get to perfect the more often you check, but just getting it off the edge should be your goal, you can get into trouble chasing perfection.