Cut out firewall from full size plans out of .25" thick plywood. Laid up 1 layer each side of BID and installed blind screws. I used a method I found on another builders sight of slotting the heads of the screws and also the firewall using welding wire to prevent the screws from spinning later. Screws were floxed in place then one layer of BID was laid over the aft face of firewall.
