Decided to co-locate the Andair In Line Filter with Check Valve (70 micron PTFE, part no. BLF375#1) next to the Brake Resevoir. By doing so, a single backing plate will work for both. Using .032 sheet I fabricated the backing plate by first bending both long edges for rigidity. Using the existing holes for the Brake Resevoir for location, the pattern for the Andair Filter was cut next. This was then transferred to the firewall. Cutting this large of a hole in the firewall stainless steel was not fun. I drilled a bunch of small .040 holes around the perimeter then snipped the inside out. Next a dremel with a grinding stone was used to smooth out the edges. Finally, I located the rivet pattern and deburred, dimpled, primed then riveted in place. Turned out well.
