ViaCAD is an excellent way to model the Zenith. You can model every part of the aircraft very accurately using a variety or combination of methods. Sometimes you may have to try different approaches to see which works best for the component that you are modeling.
For the sake of accuracy, if I were modeling something I truly wanted to build, I would do every thing as a solid. I would only use surfaces for when I'm doing concept modeling, such as just trying to see how something would look or to create illustrations. Surfaces do not have volume or depth. If modeling a wing skin, for example, the thickness of it will be important to your dimensional data. Also, having it modeled as a solid (even though a very thin solid) will give you the volume information so that you can calculate the weight or density of that part.
When I'm modeling something with different parts or components, I usually create a folder for the project. Then, I model all parts individually as separate files and then import them into one file for assembly. Many times, I actually model all parts in one file and the copy them to separate files later. That's one thing that I love about ViaCAD is that I can model multiple parts in the same workspace.
You will find that ViaCAD is great for modeling just about anything. However, when modeling something as complex as an airplane or car body (
http://forum.punchcad.com/showthread.php?t=3261), the design work requires a certain amount of strategy to figure out how to get from Point A (the idea in your head) to Point B (the 3D model). There are so many great tools featured in ViaCAD, you will find there may be multiple ways to create the same thing. The biggest issue will be to find the method that is easiest, fastest, most accurate, etc...
I guess what I'm saying is that until you are fully proficient with ViaCAD, don't be surprised if you try modeling something one way and then end up trying again another way. That's normal. After you've had a lot of practice with ViaCAD, you will learn quickly the best way to model things.