The cowl over the engine attaches to the fuselage via piano hinges placed around the firewall. Hinges were cut to length for the upper, side and lower firewall locations. Shims made of 2420 steel 0.024" thickness were fashioned and placed between the hinges and the flanges of the firewall. Needed to dimple the shims and machine countersink the hinges holes to allow the fuselage rivets to remain flush. Used longer rivets than called for because I had placed proseal between the fuselage side walls and firewall.
