Why not make your own search page and edit public_common.pl to link to that? What I'm doin for my main page is pretty much just that, just steal the html code from the linked search page and throw it into Front Page and format it how you want it then put it on your main page.
Downside to this is that is you do it quick and dirty it won't show any other parts of your board on the page, but it'll get what you're goin for done... You can see my sample at
www.undergroundnews.com. What I'm using is:
<!-- Start BBS Scan -->
<form action="http://www.undergroundnews.com/cgi-bin/ubbcgi/ultimatebb.cgi" method="post">
<p align="center">BBS Scan
<input type="hidden" name="ubb" value="search_tng">
<input type="text" name="search_words" id="search_words" size="11" maxlength="35" class="formboxes">
<input type="hidden" id="match_all-no" name="match_all" value="no">
<input type="hidden" name="search_forum" id="search_forum" multiple="multiple" value="ALL">
<input type="hidden" name="search_in" id="search_in" value="ALL">
<input type="hidden" name="search_date" id="search_date" value="ALL">
<input type="hidden" name="search_user" id="search_user" size="25" maxlength="35" value="">
<input type="submit" name="submit" value="Scan" class="buttons">
</form>
<!-- End BBS Scan -->
You can change
<input type="hidden" name="search_forum" id="search_forum" multiple="multiple" value="ALL">
to
Or you can use the select statement and list the forums like they are on the search link.