Hi,
I Advice you to set up a dynamic site to site VPN between the two spoke locations. If there is traffic for these sites it dynamically setup a site-2-site npn between this location. In stead of using the hub to connect to the other hub location.
The best way to set this up is with the Cisco Router SDM. You can downloa this tool free from the Cisco website. With this GUI it is very easy to set this up.
Good luck.
A/