Glad it worked! Sorry I was offline for a few days there- wasn't able to answer your second question. I have the original Superglow system, so my knowledge of Wilson switches is mainly as a backup plan in case something really expensive or NLA goes wrong with the Superglow...
You've answered your own question. To get 24 volts to the plugs you need to rig a circuit in series to both batteries.
If you don't know the difference between parallel and series circuits, please have an electrician do the wiring for you.