My system is 12 v., so.... I have a board made back about 25 yr. ago, which I still use for part of my system. It was originally my total controls: relay, fuses, distribution center, diode, etc., and all-in-one thing. I have since broken my system into 3 sections, two run by MX60s and one the old board. Ok, the "board" I set into a steel elec. box, but the surface of the board is some kind of "hardboard" product, a pressed-wood stuff. All the components are bolted or screwed onto it. I have never had any problem or scares with it, and I think plain plywood would work just as well. I will say that over the years I've altered the thing many times, upgrading fuses and diodes and etc. Each time I did, I insulated the new component from the board, just seemed like the thing to do. As a previous poster said, the wood is flamable, a bit, and as time went on and I upgraded I took that into consideration.