3D Printer - Better for the Inside of Models, not the Outside?

I'd mentioned last time that the Makerbot did an admirable job of making the pyramidal roof for the Drive-In tower trivial. Rather than figuring out angles, cutting forms, then carefully piecing on the outer skin, I just drew the shape I wanted, printed it, and was done. A bit of spackle to smooth things out and a coat of tar-like paint made it look just fine.

But a simple pyramid's easy. What about something more complicated - like a pyramidal roof with an octagon in the middle supporting a tower? After all, I'd had to do that to build my model of the Rio Grande gas station near Santa Barbara.

So I dashed over to SketchUp, drew a version of the tower in about an hour (mostly trying to figure out how to build the dome), printed it, and got the result seen to the right. The dome got a bit squished because the plastic couldn't cool before the next layer was applied, but it's not too bad. The tower's still a bit rough and not-to-scale, but I could scratchbuild that all out of bits of plastic. However, getting the roof lines and the octagon base is much more trouble. For the model on the left, I think I used a hunk of balsa wood for the octagon, and fit the roof pieces and underlying forms during a few hours of further work. I'd much have preferred to print out the rough roof shape and octagon, finish both with a file, then apply the roof tiles on top of that base.

I've heard about people building structures this way in the past. They would make a substructure from a chunk of wood using a table saw, then glue the walls and roof onto that chunk. Here, I'm just making that process easier, and I don't have to try to keep my fingers away from the table saw's blade as I set up awkward cuts on a small piece of wood.