I just thought I'd pass on Stephanie's response, as she couldn't post to the list:
> It looks like the SIGPLAN class file has gotten out of sync with the paper requirements and
> is producing a slightly too large textblock. I just checked the template (filled out with random text)
> against the format checker. It fails.
>
> In this situation, it seems wisest to go with the class file instead of the stated height requirement.
> I've upped the format checker to a max 9.5in height to account for this discrepancy.
Hope this helps,
Wouter