Once you have the paper template cut as close to the right size, you transfer the outline to the 0.025" stock and cut outside the lines (you can't ever make it bigger!). I used only one of the two reference holes from the hinges so I could still give myself some wiggle room for the final positioning. After clecoing through the first hole, and adjusting the location of the panel over the cowling opening, I them drilled through the hole in the hinge. Then you work your way up the sides of the fuselage and nosebowl, slowly, until everything is buttoned up tightly with clecoes.
Image 3 shows the 0.040" channelI bent up to act as a stiffener fore-aft, and to accept the quarter-turn fasteners (A.K.A. camlocs) that will hold the upper panel in place.