Hi, I may get shot for suggesting this, but has anyone considered
the possibility of sealing the internal wall of the lead tubing?

Many moons ago I was faced with a set of tracker bar tubes that
were displaying signs of internal decomposition and replacement lead
was not an option available at the time.  And, not wanting to use
plastic, rubber or neoprene as an alternative (there's a surprise!),
I experimented with a dilute solution of Uni-bond.

Uni-bond is a water based product similar to your PPCo 320 or Elmer's
glue.  It has the advantage of being flexible when dry and impervious
to moisture.  Using a syringe I flooded the tubes with the solution and
then applied compressed air to expel the excess glue and to dry the
inside of the tube.  Re-attachment of the tubing was a simple affair;
I also spray lacquered the outside surface and in effect the tubes were
sealed both inside and out.  To my knowledge the player is still
operating to this day with the original lead.

The same problem also occurs with the lead or composition metal elbows
common in many players; the trick with these was to spray them with
lacquer and then with polyurethane.  This usually did the trick.

Cheers, Paul Camps, UK