Anything that would permit the rubber boot seal to do it's job will certainly help.

I'm wary about applying epoxy to this area though, and the center part of the seal contacts the rotating part of the drum that affixes to the throttle lever.

It may well be that the engines I have that do not exhibit any problems have a better boot seal, though in some cases I've tried swapping in brand new carbs to see if there is any improvement.

Dunno... but it seems like there is something ST is missing in it's design to eliminate the low/mid problem altogether.

The "half moon" fix works like a champ on several aflicted engines I have.... but I know all I'm doing is leaning out an overly rich low end, favoring better transitions.