No problem; I also realized I did not say anything about where to change those sizes.  On the CVS HEAD version of
acs-subsite/www/resources/site-master.css they are set smaller via: 
h1 {
  font-size: 120%;
  margin-bottom: 12px;
}
 
Already so I would guess that would be the right place 
to change other sites, although it depends a little on 
what the base version of OpenACS it is since the resources 
dir was not added until 5 I think (not sure).