Thanks for the additional info.
I might get the neck done after all, even though I can't see any symptoms of it having shifted other than the action height. It's a simple mortise joint and a floating fretboard, much simpler to detach and shim than your typical flat top dreadnought. A neck reset every half-century or so doesn't seem excessive.
I'll keep you all posted, particularly about the results with the light strings.
-Glenn