I was showing someone how to create a custom page template with Thematic and realized this is probably a common question. I'm sure it's answered somewhere in the Thematic documentation or on the forum- but if you're curious about how to make a full width page template, or any page template for that matter, I wrote a post about how to do it:
http://wordpresstheming.com/2010/03/custom-page-templates-thematic/.