We'll I've made my first real mistake so far on this build. Note the image below. The double-thick rib moulded into the flap is that wide so that it can accomodate both the hinge and the flap horn. The intention is to drill the flap hinge off to one side, leaving room for the horn along side it. Trouble is, I chose which side to favor the hinge using the plans... which are showing the bottom surface... a fact that I missed. As a result, you can see that the horn would like to be directly behind the flap servo arm, but mine is offset 3/8th or so. No huge deal, but if you are building one, pay extra attention to which side you drill the hinge on. Use the cutout for the servo pocket to guide you to the correct side!

-G