Mike, take a look at the articles on the link that's also at the top of the page. http://www.rcbatteryclinic.com/
I went the parallel battery path with 2 switches, it doubles the path of power to the RX so it halves the chance of failure. Red also explains why the chance of the bad pack taking the good pack down is remote. Two smaller batteries (for about the same total weight) may be easier to fit in your model than one big one if the install is a squeeze. - John.