Tim...I like it! As for the long back seats, my '69 also has armrests on the side next to the barn doors.
I need to see how you are mounting the base on the armrest side. Since i used to the bracket to space the seats away from the aftermarket rollbar, the one mount hangs out over the wheelwell. I guess I should post a pic to explain.
Bingo...i like that bracket idea. Assuming it will hold the weight of a normal sized person. I was thinking about building a toolboxwith speaker enclosure that the seat that mount will rest on.
Thx for the pic!