First of all, the method you describe is totally unnessesary for the OP's situation. A simple turn and rethread will suffice.
Turning the shank down to a small diameter and then adding a sleeve compromizes the strength of the chamber. No matter how tight the threads are on the sleeve and the fact that a filler/adhesive has been added, the chamber will expand more than if it was a solid diameter. I know this because I have also done it as an experiment. After numerous jolts of high pressure and rapid heat dissapation, the Devcon starts to deteriorate to the point there is no solid joint anymore. The chamber slowly grows in diameter under pressure and contracts at a greater rate than the cartridge brass does to the point where extraction is very difficult even with moderate loads.

Gene Beggs ran an experiment using a sleeve with 2 different rate thread pitches to index a barrel with out affecting headspace. His sleeves were much thinner and left more meat on the barrel shank. His tests ran into the same problem. The barrel indexing theory was proven, but the problem lied in the fact that the extra joint allowed for more case expansion.

If it works for you, fine, but there are no reputable gunsmiths that would give this a nod for an acceptable practice.