Adjusting the vertical placement of margin notes

[R. H. van der Gaag]

I write most of my longer copy using the (beautiful and eminently readable) Tufte Book and Tufte Handout document class. One advantage of this is that footnotes are displayed as margin notes. If a note is added near the bottom of the page, though, this causes the note text to extend beyond the lower edge of the main text column. Obviously, the note should either scoot upwards, enough for its last line to land at the same vertical position as the main text column’s last line, or the note should break off at that vertical position, and continue on the next page. But I don’t know how to accomplish this.