[elhigh]

Have you looked at sealed batts to go under the rear seat, where the stock location is/was? Or maybe fitting a couple under the front seats? There's all kinds of places where you can stuff in a battery or two, and after that it's just a matter of running GREAT BIG CABLES.

Man this looks like a fun build.

Reading Hot VWs magazine, they talked about finding a solid 2mpg improvement by adding a small wing just below the rear window. It evidently helps keep airflow attached farther down the back of the car, and then give a clean separation. If you're not worried about keeping it looking stock and factory, you might want to do that too - mileage gains in gas are watt-hour/mile reductions in EV.