Only things I would add here is the industry uses Paxolin as a construction medium for electrical switchgear, it's water/moisture/fire/heat resistant, it can be drilled, cut and meets all approvals for intended use, ply really doesn't! and I would ensure there is a fused/MCB protective device on all your control circuits, an unfused 400A bus supply will make short work of destroying your control wiring if a fault develops.