Tourweaver doesn't allow for custom buttons in fullscreen mode unless you modify the fullscreenbar.fla file that is located in the "Resources" folder.
Supposedly the new release/update just released contains a selection of fullscreenbars to choose from. Download the latest build and take a look.
My personal preference is to be able to build a menu in "standard" mode and have it applied to my fullscreen version if I choose. Unfortunately this is not the case to date.