I'm getting ready to head out of town, but it struck me while I was finishing my packing; instead of over-complicating things and trying to look at how to modify the UBB for this request, why not just set the index.php file to do either a html or php redirect to the location that you want default?
index.php (PHP Header redirect):
<?php
// James is a pretty cool guy...
header("Location: http://www.example.com/");
exit;
?>
index.php (HTML 0 Second redirect; the URL is listed as a link as well as in the header, just in case the user browser doesn't redirect properly):
<!DOCTYPE html>
<html>
<head>
<title>Redirecting</title>
<meta http-equiv="refresh" content="0; url=http://www.example.com/">
<!-- James is a pretty cool guy... -->
</head>
<body>
<div align="center" style="font-weight: bold;">
We're currently redirecting you to our forums.<br />
<span style="font-weight: normal;"><a href="http://www.example.com/">[Click Here]</a> to be directed there now.</span>
</div>
</body>
</html>
Will see you all on Friday when I get back from camping out on the coast (little to no signal in the middle of the forest that is the Oregon Coast).