I trimmed both the filtered air box and the NACA vent along the scribe lines, then marked a center line on both and on the fuselage cutouts. I fit both, using a straight edge (the trusty 6" steel ruler) to align them more or less properly. I sanded the area of the bottom cowl where both would be bonded, did likewise to the two units, cleaned with rubbing alcohol, mixed up some epoxy and flox and bonded both to the bottom cowling. Then I added some epoxy to the gaps from the outside, and put packing tape over them per the instructions. Once cured, I'll sand a nice transition from both. I then put the top cowling back on until the epoxy has cured.