David,
Yeah, our Page Tab on the SourceCoast page is cutoff too. We're in a transition right now to a new template that will fit the width there, and plan to have it fixed over the next week or so.
Unfortunately, the issue you're having is that the Canvas view (apps.facebook.com) is treated differently than the Page Tab view. This is done by Facebook, and not something we can change. The Canvas views have the option for a fixed width, or fluid, as you know. The Page Tabs only have options for widths of 520px or 810px. There is now way to 'grow' beyond the 810px width requirement for Page Tabs. The 810 width was actually just introduced with the timeline. Previously, all Page Tabs had to be 520px, which was severely limiting.
The width restrictions are one of the main reasons that JFBConnect has the option to force the use of a specific template for either the Canvas or Page Tab views. Unfortunately, you'll need to use a template with a width of 810px, or modify your current template to accomodate that size.
Hope that all makes sense. We wish the Page Tab views had the same 'fluid width' option as well, but since there are 2 sidebars on Page Tab, that's not easily possible.
Alex