Need guidance on changing Countrywide Navbar

[Contours]

I'm attempting to implement the Countrywide Horizontal Navbar with these changes:

Font: Trebuchet >> Arial 16
Font color: white for both layers
Navbar width: 600 pixels
No gradient on Mouse Off buttons
Button width according to text (so they're spread out across the 600 pixels

I have now failed so many times that I've lost count. I've been following "Ungrouping, editing and regrouping" ... and, indeed, I can Ungroup for Editing, change something like the font, and then immediately regroup as a NavBar (Create Navbar). But, invariably, one of my edits—or some combination—derails the whole process and Xara refuses to save my result as a Navbar (with a fairly non-descript message).

Can someone please list the steps in carrying out the above changes, with the points at which the Apply Soft Group and the Create Navigation Bar operations should be used? The attachment shows my starting point, immediately after the first Ungroup for Editing. I'm running Pro X9 on Win7 Pro.

Thanks in advance for any help.