Hey Rad riders!  I'm planning to add a second battery with a datex2 and was wondering where folks have added a second battery on the Rad Runner?   Some options I'm toying with are under the passenger seat (ideal)  or on the front downtube, which would bum me out as I love the step-thru convenience of my RadRunner+.   Bonus points for pics of your second battery!   

Thanks and stay Rad!