Graham
Try the notation window options. it's the OPT button on the notation screen.

You can set the font sizes for text, lyrics, chords and title as percentages of the font size in the PRINT OPTIONS, and as far as I have seen, they do not change the bar height. I have my font size set at 18, but my lyrics set at 140%

You may have to play around with the combinations, but it does work for me


BIAB for Windows Version 2019 (643)
Windows 10 (1909)