I will point out that JB is used just to maintain position. There is metal to metal contact at all times between the spacer and bottom of the arbor hole. JB obviously flows into any voids but a ring of contact is present which is why I use a "pan head" ( rounded) screw head as the contact surface for the bottom of the hole. I add two "started" holes ( one on each side of the arbor hole where it transitions to a cone shape from the end of the drill bit. These "semi-holes" anchor the spacer should any of the JB fail.
It, by the way, can be drilled out. Can't for the life of me figure why a too short arbor would be preferred over a "corrected " arbor fit . . . As far as I know, I haven't had any failures. I'm not saying Shotgun Dave's isn't good, ( it is) mine is just quicker for me.
I just did a pair of "Tame Bill's" that had been done with a brass button (i.e. Pettifoggers article). I had done some cap guns for him and he said my fix was superior with the s.s. setup.
No matter what method is used, it's good as long as it works.
Mike