As per the instructions on page 161, I drilled 4 1/2" holes for the cabin vents. But, the only covers I can find are a maximum of 5" in diameter, with 4 5/8" between the mounting holes. That means I have only 1/16" of wood all around to drill my mounting holes into. That's not going to work.
So my plan is to fashion plywood flanges to go around the vent covers and use very short screws to attach the covers to the flanges from the inside. The flanges would match the ones around the port lights. The hitch there is that the best way to cut the flanges is with a router mounted to a circle jig, but the only ones I can find cut a minimum diameter of 10" (makes sense because of the diameter of most router bases). So what to do?
I have seen pictures where others have made similar flanges. I have a jig saw that might do the trick after rough-cutting the plywood to the approximate size. I'd have to rig some kind of centering pin. Any ideas?
Or, if someone knows where I can find a 5 1/2" or 6" vent cover, that would be an easier fix.