Actually, I just thought of a PMX-only solution: put a dummy blank (with one
bar of music) after a Vx and a forced page break at the end of the last real
page.
Ah. A solution that is simultaneously kludgy and elegant. (Kludgy in
that it achieves the desired result in a roundabout fashion, elegant
in that it is easy to use *and* has no undesirable side effects other
than using a single extra sheet of paper). I don't even need to use
the PMX-only part of it--in M-Tx I can just add a %%P2Ln and a whole
rest.