I didn't think to ask before, but is it actually the nosecone, or is it the canopy? I couldn't really tell in the picture... If it's the nosecone, I agree, vacu-forming is NOT the way to go! [X(]

If it is in fact just the canopy, and assuming it's not critical to the structure, then vacu-forming one is one option. I'm fairly new to it, but there are lotsa threads on RCU that explain it. I use a shop vac for the vacuum part, a large plastic box with perforated circuit-board material covering the top as the work surface(roughly 8X10). I've also seen bigger ones that use pegboard as the work surface, but I don't need parts that big. I just use scrap wood(whatever is laying around) for a frame for the plastic, and use my heat gun to carefully heat the plastic. Then with the vacuum running pull it down over the form. The plastic only takes a few seconds to cool and harden, and will work for most shapes. It's quick(after you make the form), easy, and cheap. (after you figure it out).

Also, if it's not structural, then foam can be shaped to fit to either leave as is(not sure how you'd attach it), or you could even use that as a plug to make a fiberglass part.

I like the fiberglass method that BMatthews suggested - that might actually be better in this application. That looks like a very nice plane - absolutely worth the extra effort.