I decided my airplane needed some identifying insignia, so I set about figuring out how to do that.
The tail surfaces are flat and present no difficulty, but the fuselage and wing surfaces have curves that resist direct drawing techniques.
The maltese cross image was projected onto the slightly curved sides with a technique demonstrated in a video tutorial by Aidan Chopra, author of "SketchUp for Dummies".
For the crosses on the wings, I tried a plug-in tool that allows drawing on curved surfaces, but I couldn't achieve the kind of precision needed to complete the design successfully. In the end, I used the same technique that allowed me to cut the hole for the cockpit.
A form with the desired profile is pushed through the surfaces, the two objects are merged, and new edges and surfaces are created. Once an area is enclosed with a continuous perimeter, materials and images can be projected or painted onto it without leaking onto the contiguous surfaces.
I've also scaled back the cowling a bit to give the plane a profile a bit more in line with photos I've seen of it. I'm planning on tweaking a few more details, laying on some color, and hope to wrap up this project in a week or so.