Depending on where you put it [top or bottom of original], the second navbar will center with the actual forum cells or header template cells. Depending on the size/styles of the forum, this may affect the actually cells the forums are in. Also, it might depend on spacing/how many links..may affect the actual size.
Did you use a mod? Or copy the template from the original and just edit the links? [probably easiest way]
Might want to just copy and paste another navbar into the navbar template and edit the links. SImplest way, thats what I did. Just copied the original, pasted it, and edited the links.