The forward side of the fuselage will attach the firewall to the forward main spar via the floors and exhaust/utility tunnel.

The exhaust/utility tunnel is made up of two parts, a stainless steel inner tunnel that is an extension of the stainless steel firewall and an outer aluminum tunnel that encloses it and a space for fuel, rudder cables and electrical runs.

The first two pictures show the aluminum outer tunnel walls and some pieces that attach to it or the firewall.

The last two pictures show the lower right firewall piece being dimpled.