when using an inflexible document class, one is often faced with the warning
Underfull \vbox (badness 10000) has occurred while \output is active 
on pages that contain no display math.
frank mittelbach quotes from the companion (2ed) regarding page
specs that are "too rigid". the recommended (and obvious) approach is to build in
the same suggestions, to add flexibility, are given in What are underfull hboxes and vboxes and how can I get rid of them?.
the document class in question was constructed (intentionally, if
short-sightedly) with no allowance for stretch in the
between chapter title and text, and in a few other locations.
furthermore, an option permits the change from
body text so even if the
\textheight is an integral number of
lines in one size, another size will not meet the criterion.
\vfuzz one can specify a small allowance which, if not
exceeded, will suppress overfull box messages. but there isn't
any equivalent for a negative allowance.
i've checked the
etex manual (the latest, dated 1998/03/04) and that for
didn't find anything useful. i've looked into the
but it wasn't obvious how one might work around the problem
without a new primitive.
it's not a good idea to ignore these messages in the log, since the "structural" ones camouflage the ones (usually very few) that do need to be attended to. has anyone come up with a method for suppressing only those underfull vbox messages that are off by only a couple of points?