Encourage A4 to page break before a tune. This enourages page breaks to happen before tune start, and not between the tune image and any following wording. Also move the vfill to the tune start. That way, if the break does not happen, the vfill will, and the following tune will be spaced down to the bottom of the page if it's the only other tune on the page. Otherwise everything tends to clump at the top of the page.

X:1
T:Tip Top Polka
M:4/4
L:1/8
Q:160
K:G
Bc |: \
"G" d2d2 dedc | B2B2 B2GA | B2B2Bcd2 | "D" A6 AB | "C" c2c2 cdcB |
[1 "D" A2A2 A2AB | cde2 d2c2 | "G" B6 c2 :| \
[2 "D" A2A2 A2G2 | FGAB e2f2 | "G" g6 ||
|: ef |\
"C" g2e2 e2ef | "G" g2d2 d4 | B4 A2 G2 | "D" d6 ef | \
"C" g2e2 e2ef | "G "g2d2 d4 | "D" Bcd2 B2A2 | "G" G6 :|