On all of my scratchbuilt/kits I tend to glass in a piece of 3/4-2oz cloth over the firewall and extending about 2-3 inches back, use finishing resin, 30 minute epoxy, wet sand afterwards and you won't know its there after covering. Adds strength and fuelproofs at same time. Use any left over resin to fuel proof the inside around the tank area. Course this is in addition to the triangular stock on inside that is epoxied to firewall. Just a little extra insurance, and since you need to fuelproof anyway, all you are adding is a piece of fiberglass cloth.