A few questions regarding profile fields and if conditions.

[Blind Guardian]

Could someone please explain to me how the user-profile fields work using if conditions?

I've been working in a few modifications on my forum and wanted to give members the option to show or hide them via their userCP options. I finally got one to work (I added in a row above the announcements that links to forum-wide rules), but I used a multiple-field checkbox for that (although only using one condition) and finally worked out I needed:

<if condition="empty($bbuserinfo['field25'])"> </if>

I cannot work out what to do for multiple fields, though. For instance, radio buttons. I've tried various variations of the above, such as:

<if condition="$bbuserinfo['fieldX'] == 1"> </if>

But I never seem to pull the value correctly.

Also, while i'm asking, is there a way I can set the default for a checkbox, as in whether it's checked to begin with or not?

Any help would be appreciated.