I recently acquired a vintage Sheaffer Balance lever-filler and the section no longer friction-fits in the barrel well enough for it to stay put. It's not a huge difference - it's just enough that it won't stay put. I don't have much experience with celluloid lever fillers. I'm about to put a new sac on it and will test it well before I put the barrel back on so I don't anticipate having to open it for a long time.

Should I use shellac for the section/barrel junction? Or what?