As far as I know, you cannot make the web part grow dynamically with the
contents. At least, any time I tried it (spent about 2hrs on it one night),
I couldn't get it to work. Would love to have it work, of course, so if
anyone knows how, please share.
Best I could figure was to estimate about 2.5x the height of the "collapse
all" view, expecting that people generally wouldn't expand more than that
before clicking something.