Use ly:one-line-auto-height-breaking #68
Description
This function was introduced in LilyPond 2.19.x. It's like ly:one-line-breaking except the page height is automatically modified to fit the height of the music:
http://lilypond.org/doc/v2.19/Documentation/notation/page-breaking#one_002dline_002dauto_002dheight-page-breaking
Using it would allow for simpler code (no cropping needed for vertical margins) and it would let users more easily/quickly fine-tune margins, by getting the pdf right before producing a video (more WYSIWYG). Worth considering at least.