The only way I can see this working the way you want is if I render the page smaller in anticipation of the next song bar being shown. That way it fits the page perfectly while the song bar is shown. I'll work on getting this fixed.
UPDATE:
Should be fixed in v1.5.3. I reduce the available page height by the next song bar height before rendering so the pages fit properly into the available space.
UPDATE:
Should be fixed in v1.5.3. I reduce the available page height by the next song bar height before rendering so the pages fit properly into the available space.