My mast has one foot section of PVC conduit every 4 ft or so bonded to the
interior wall with exopy (or some type of goop.

At first I couldn't figure out how they were installed.. Then I noticed that
the mast is in 2 section with a doubler and welded at about 25 ft up the
mast. Perhaps they used a method like Glenn discribes or a PVC pole to push
the conduit sections into position.

BTW, I have seen some mast extrusion that have a 'dove tail' grove (kind of
a internal track) on the inside that would allow a series of clips to be
used to secure the conduit in place.

--
My opinion and experience. FWIW

Steve
s/v Good Intentions