Yes, all above true. Got the copper rounds from the "bopper" on Etsy, originally recommended by O-L. I have a supply on hand of various diameter copper rounds, I believe 18 gauge is the max thickness they make. You can message Beverly, shop here: https://www.etsy.com/shop/Bopper, and ask for any custom sizes or quantity. She has the best prices I could find, but these copper rounds aren't made for what we use them for, so they aren't perfectly flat. I usually sand them down to at or near flat before installing them (basically they bulge up - one side bumps out in the middle, the other side has a center indent. Since the pill is brass, could reflow the disc to the pill. For alum pills, I use Arctic thermal epoxy.
I had the emitter bare, reflowed to a 16mm Noctigon. The Noctigon needed no trimming/sanding - fit perfect.
The driver is this: https://budgetlightforum.com/t/-/31102. Sanding down to 16mm gets a little hairy. The grnd tab of the 7135 was interfering with it sitting on the lip in the brass pill, but the pill has those 2 cutouts in it. So, if you align the 7135 tab to one of the cutouts, it seats down perfectly.