My firewall is thicker (ACP Composites 1/4" end grain balsa with carbon fiber laminates on both sides)
That is a good idea. I used 1/8" end grain with CF and it needed a little reinforcement later with a couple of CF rods because it was flexing a bit under full power, which is not acceptable at all. However, the CF rods did the stiffening trick and it is still solid after nearly 500 flights.