[Martin CX]

I'm not sure if this is what you wanted, but if you subsitute this:

<tr>
	<td bgcolor="{firstaltcolor}"><normalfont><b>Invisible Mode?</b></normalfont><br>
	<smallfont>Selecting yes allows you to surf the forums without appearing in the 'Logged In Users' list.</smallfont></td>
	<td bgcolor="{firstaltcolor}"><normalfont>
		<input type="radio" name="invisible" value="yes"> yes
		<input type="radio" name="invisible" value="no" checked> no
	</normalfont></td>
</tr>

with this

<input type="hidden" name="invisible" value="no">

in the registeradult template, people won't be able to choose to be invisible. If you do the same in the proper user option template and you should be set.