I use what mitch posted on the 30 AA I did years ago. I found you should cut the roll in half and tape each half to the frame rails, then let it set for a day or two to normalize, then mark and punch the holes. I unrolled the welt and taped and punched the holes in an hour, but when I went to bolt parts on a couple days later I found the stuff had to be pulled hard to get the holes lined up again. It shrunk a bit.
The respected voice of experience once again offers his great advice ! This man speaks with experience to back it up.
Wayne