Thanks to Lens Hacker I've been able to rid the J3 of the "notchy focus". A clean/re-lube of the helix fixed that. Thanks for the webpage!
I actually DID run some film as a focal point check when that was done. I set up 3 targets about 1/3 meter apart and focused on the middle taget from 1, 2 3, 4, and 7 meters away. The focus favors the further of the 3 targets at 1 meter. From the rest of the distances the OOF targets diminish according to distance from target.
From this, I assume I could use anothr shim in the focussing mount. I believe I'll just give the focus ring an extra small turn toward closer when shooting at close distances . Unless, of course you can tell me the thickness of a shim required to shorten the focus by 6" @ 1 meter