After another several hours of searching and organizing, I located the strip that had been eluding me.

Clecoed on the upper forward fuselage skin.

After placing the canopy structure in place, I checked the alignment of the canopy skin and the upper forward fuselage skin. It's not too bad here in the middle.

...but at the 10 o'clock and 2 o'clock positions, the canopy skin sticks up about 1/16". Many posts on VAF refer to these "air scoops" and lots of people have struggled in this area. After puzzling on this a while, I decided I'm going to remake these skins from a single piece of aluminum which I will then split and file / trim. Also, I'll be modifying the curvature of the quarter-round ribs of upper structure by cutting off the top flanges and riveting on new flanges. It'll be easier to understand as the progress becomes visible.