Decided to mount the NACA ducts with screws and nutplates so they are removable. Used .032 sheet and traced the outline to make a reinforcing doubler for the plastic duct. Measured the flange and marked to make inner outline. Cut out shape on the bandsaw and smoothed on the sander. Split the pattern and cut out the inside, filed and sanded to fit. Did the same process for the other duct.
