mod rewrite for a different theme?

Hi

I'm pretty new at this whole SEO thing, and I downloaded the phpbb SEO pack. I've applied the mod_rewrite mod that was in it, and it works great for subsilver. I'd like to get it working for the 'grey' theme that I use as the 'not logged in' theme.

As far as I can tell the only files changed (other than robots.txt and .htaccess) are files in the /includes folder - which should be the same for every theme shouldn't they?

Am I being completely dense?

Thanks in advance.