Best way to compress it? Tried peening  a nail for one and it worked ok only but did not fill the angled sides completely. What the best way to do one of the ones being sold. Thanks.

Try using a longer or wider nail. I peen it wider and bigger than the hole, then use a dremil tool to sand/grind it smooth with the slope of the bolt/piston carrier. If ya do it right, other than some slight grind marks , its hard to tell where the hole was/is.

once you get the old piston out and the new one drilled,I have found that a roofing nail fits perfect. I slide it in, center it and cut with the dremel leaving about a 1/16th" on each side. then a peen it with the hammer in each side forming it to the piston(very little effort) put a fine sanding wheel in the dremel and clean it up .

I did the roofing nail and left it plenty long when I peened the heck out of it but it still left tiny gaps in a couple of places around the recessed area and it fattened the nail out a little inside the carrier and piston hole so I lost most of the looseness I had from the 1/4 turn back off of the piston. Thought I would try something different if anyone had any ideas. Thanks for the replys.