Finally back in the shop after a long layoff to move my son from rental into his own house, move my Mom into assited living and clean out her home of 47 years, and move my best friend from Ohio to Virginia.
Picked up where we left off in July with increasing depth of T-407 countersinks a click at a time until the ring sat flush on the dimples. Ended up about .009 past initial setting. Ring is flush all around inside diameter, some small gaps on outside diameter. Set up right wing tank T-407 and cut countersinks to same depth.
Moved on to drilling the fuel drain bosses to left and right tank skins. Deburred all holes.