FYI the Savage Flux battery boxes bolt to the E-Savage with an extended chassis with little effort.
I only run 2-3s in the e-savage max hence the single box.
This is mine... FLM extended chassis, Kershaw Designs e-savage shocks (I think they are from CEN MT), Novak HV-Maxx with 6.5 motor and a few more goods. It has been a good truck. Not the best, but its fine under 2-3S power. I rarely break anything on it.