Here is my plan:
Take the stock plug 5/8 or 7/8, no matter. Remove all the metal from the top of the plug flush with the flashhole. Drill and tap it for a 1" long 7/16 -14 ss hex head bolt. Drill a.2460" hole for the primer all the way down the bolt except for the last 1/4 inch. Then drill the rest of the way with a #65 bit for a .035" flashhole.
Place the bolt in the drilled and tapped plug with a primer in it and some loctite or jb weld on the threads, then put it in the gun. Then adjust the bolt up for headspace until it 'just closes". let the loctite/jb weld set overnight then remove the plug and tig weld around the the bottom of the bolt head. This will allow for a 5/8 or 16mm socket to put it in and remove it.
I thought this might work well since Hubbard said the tolerences on these guns can be very different. Being able to screw the bolt in or out would customize it to your specific gun.
I have found that the bolt does have some slight movement in a nut so to counter that I will be putting teflon tape around the bolt before adding the loctite/jb weld.
I have the plug and the bolt and my coworker has the bits and tap. Just need him to get the time to put it on the lathe.
Will post results.