I bought a small sheet of 0.005X4X10" at either Hobby Lobby or Ace. I cut a piece about 1/2" square and scratch up the backside with coarse sandpaper and/or file. I also make sure there are no sharp corners or edges to bind via hand filing. I bend it slightly to conform to the inside AF. I clean roughed side with IPA. I have used either 5 min epoxy or CA to adhere. I use a piece of slick paper (wax, etc) on one side so the glue won't stick and then C-clamp it to cure. When done, drill hole for shear pin. I still put a little CA on the cardboard around the hole. But this has worked well for me. You'll want to test fit to ensure no binding.
