Installed the alternate air door in the snorkel. Note- If you cut the hole for this per the print dimension, it's in the wrong place. Instead of 3 1/2" from the lower lip of the filter box it should be approx 3 1/2" from the upper fwd edge. If you get it too far aft, the edge of the assembly would be hanging off in space behind the radius at the aft corner of the snorkel and you wouldn't be able to rivet it in a later step. Anyway, I basically centered it on the flat spot which seemed pretty intuitive. Once I mocked it up it looked like that would work nicely so thats what I went with. Cut the hole with the tried and true method of drilling a bunch of holes, connecting the dots with a dremmel cutoff wheel, and then trueing it up with a flapper disc. Ground the sharp corners and de-burred the base flange, installed the required nut plate, and epoxy/floxed in place per print.