I just modified my board to have the box in the middle. I can still paddle square stance fine and the swing weight is much improved. I can now pump the sup board and it feels almost as if it isn’t there which it what I was hoping for.
One disadvantage on my narrow board is that if I feel I am losing sideways balance, I can often recover it but with the battery in its new location I have less time to recover on the sideways roll. I’m sure I will get use to it as the more natural feel and weight distribution feels great.