Without knowing for sure that it is required, I hesitated to install the firewall recess but opted to install it because that way it works either way. Eliminates indecision. And cleans up the shop.
Drilled out pilot holes in corners, enlarged with Unibit, and snipped the stainless steel firewall out to the size required by roughly measuring the recess and determining the existing angle structure (and reviewing Dan C's photos). Cleaned up the edges with a file and drilled out most of the existing rivets, carefully. Bottom of hole had no angle, so fabbed a 3/4" x 3/4" stiffener. Backdrilled the rivet holes into the recess (taped and held tightly on the opening) while installing clecoes as it progressed. Favored the RT side of the opening slightly to accomodate the rivet shop heads of the rudder pedal center bracket.
Two of the rivets were not removed because they are located exactly between two sections of the edge of the recess. So they will remain in the underlying firewall surface. Added two additional holes along the top edge to secure the corners of the recess.
Later will have to relocate the rudder pedal cross tubes because they hit the back of the recess. This will require about 3/4" aft relocation of the most forward position. The far aft is for short pilots and the middle for medium pilots, while the long legged pilots will lose 3/4" of leg room.
