I do similar to Sabardyn
I set the Top and Bottom Margin on the Chapter heading (for the block for multi line chapter heads) style to 2em. IMHO a nice balanced whitespace without wasting huge amounts of screen.
I mainly use Top margins in the <p> body of the text as a bottom margin can cause MRSDK to create a 1 or 2 line orphan (needlesly) to accomodate the margin at the end of the last line.
Note: I am
swipe challenged, my reader has page turn buttons so the
past end of chapter does not happen frequently to me