I'm with Bobbinwinder. Wide divider strips would take away from the focus on the braids. How about a 4-5 inch wide floral stripe fabric, if you have that? That would act as a good divider and outer border, and bring it all together. Plus it would give you at least 16 to 20 inches more width to get to your queen size. Maybe adding one more braid chain would help too.
Barb