Yes, you could do that, too! Smart guy! I forgot about that one.
This way is a little more idiot-proof, though, and allows one to more easily attach the wiring harness to the two batteries (in my case, they're taped together, as there's only one battery clip in the Intrepid's control cavity) then insert the batteries and hook them up to the stock battery clip. And if you don't have room to put the batteries exactly side-by-side, you can position the second battery wherever you need it, and can adjust the wire lengths to suit.