Sweet mercy that looks impregnable.

I am however a bit concerned for the left most batter and the motor wires placed ontop of it. they are going to be a bit to close to those to motors for comfort so i need to find a way hold them down securely.
If there is any sideways movement, move the batteries a little closer to the centre, drill 2x M3 bolt holes, one either side of where the battery is going to be, thin HDPE plate with a hole at each end of it and then with a nut and washer, wind the nut+washer onto the plate with the battery in between that and the rear plate to sandwich it in is how I would do it.