I use a mini square swiss file,mostly because I'm afraid I might make the square cutout wider than the clip and ruin it.I try to sneak up on it,checking often so it's a super tight fit just like the stock cutout.
I tried 180 degrees,but it doesn't look right to me like that.I set the original cutout at about 11 o' clock,then make the slot at 6 o' clock,so the sight ends up being about 1/16'',as the original poster recommended.
I also discovered that the end cap that we are modifying is pressed in the end of the body as a separate part.I wish I could make an expandable collet tool that I could fit in the end cap piece,then expand it,then pull it out with a slide hammer.That happened accidently on one I did,and it made it easy.......just rotate the end cap with the slot in the 6/0 clock position,blue lok-tite it and press it together.No filing needed.
I commented to PSI that it would be nice to just have the bolt action end sent unassembled,so we could just press the end piece in wherever we wanted.......never heard back..
Steve