Mike,
You have brought up a very interesting topic. "Electricity" is my business, but batteries are not. I hear that many folks want to change over to 6 volt golf cart batteries, but frankly never understood why. Without really thinking about it, I just assumed that it was to obtain more capacity. I never thought about it - I was happy with the 2x12 volt batteries in my Sun Voyager. Hard to believe that could be a wives tale.
I did some online reading and confirmed at
http://www.trojanbattery.com/Tech-Su...nsDiagram.aspx that you are absolutely correct, per a battery manufacturer.
A series connection of batteries will increase the voltage (A trick to start old 6 volt construction equipment was to apply 12 volts to the starter, with the 6 volt battery disconnected!) without affecting the capacity.
A parallel connection will increase the capacity (per the above reference). Apparently, you have made a very wise choice in your conversion to 12 volts. Now, how do you make your propane hold out for more than a couple nights in cold temperatures?