I haven't done any model kits for a LOOOONG time, but this is what I'd try:
Because the nosecone is such a pain to try to adapt a mirrored image on, I would draw a basic sketch on paper, then find something with roughly the same dimensions as the nose of the plane in order to adapt the basic idea onto it, just to see what you're looking for. You might be able to find model plane noses on E-bay or something too, you never know. I hear it's also a good idea to paint certain parts of a model before you actually assemble them. I never got that memo when I was doing model kits (speaking of which, that actually doesn't sound like a bad hobby to get back into...)
Considering the size of the model, trying to stencil and reference everything from paper sketches could turn into a nightmare. It would really come down to whether your hand is more precise than paper. Paper can wrinkle, mislead the stenciling if not secured properly, and there's the pure hassle of making it, then securing and positioning it to begin with. Having the other cone/plane nose comes in handy because you'll be seeing your reference and your art piece in basically the same dimensions, so it wont be as hard to replicate the same design. If symmetry is what you're most concerned about, I'd look up tutorials on how to strengthen that skill-set. Even if it's not done on 3-dimensional space it may help to become more familiar with symmetry in general and picking up some of its nuances.
Since it's such a small surface area it might be worthwhile to get some sort of mounted magnifying glass that you can hover over the nose of the plane while putting in details too. I've never done it myself, but I'd consider it for something like that. I'll drop in more info if I can think of anything else later. Sounds like a cool idea in any case - hope to see it soon!