[Marco van Herwaarden]

A new style is nothing more then an empty placeholder. It will always inherit the template data from the level above (even with no parent set, you will be using the hidden default style for the template data).

Only templates that are modified in the current style are stored with the style.

When a page is requested the styles are merged into the style that will be used for the current page, this does not have much overhead.

As long as you remember to do all your changes to 1 upper level style and only make changes to the templates that need to be different in teh child style(s) for your forums that should have a specific template. You can set a forum to use an admin set style, regardless of the users choice.

I would suggest to use this method as it is just using the default options offered by vBulletin, so it should always work without any (code) changes if you would upgrade vBulletin.

By going the plugin route, you are creating extra code (overhead) that might break in a future version of vBulletin.