Its really not that bad. Just draw a horizontal line segment, rotate it 2 degrees (check angle against the manifold to be sure its correct, tho I'm pretty certain 2 degrees is the right value).
Put it where you want, and trim to fit. You can copy and paste for the other parallel panel lines in the nose section. The hardest thing to get used to is that its no longer a pure smooth line - its a little fuzzy and jagged because of the rotation (at least in Photoshop it is). But, you may find it looks more natural being in alignment with the manifold now. And you're gonna be reducing the opacity to what, 5-10% anyway.
Dang, I just noticed Ding Hao! has a birdcage canopy, not the Malcolm bubble like AH's '51B. I wish HTC would add both the birdcage '51B and an early '51D without the tail fillet, so skins could be put on the historically accurate airframe (plus, twice as many P-51 skin slots, muhahahah!)