At the moment, I have 2 NEST thermostats. A 5 wire Tstat wire was installed at both Tstat locations. We realized that the NEST wanted a common to properly charge so a Venstar add a wire was used to provide the common. We also have a dual stage cooling unit (Goodman). How do we get one more wire to the Tstat? Is is possible to use 2 Add a Wire units to get a 5 wire to 7 wire?