[suicideneil]

I reckon a Gmaxx strap from one end of each battery box to the other would be fine- bolt it onto the aluminum end caps either on the inside or out side, depending on how snug a fit the batts are in their boxes. Do you have the batts already- a pic would prove useful in seeing how tight a fit they are.
That and we like picks around here, as you should know..... :)