[mntmoss]

I think your practices are fine - coding even a limited prototype reveals a lot of unanswered questions in a mental model. Once you have the model, you can apply it in a theoretical sense, but in my experience it takes longer to build one by not coding than it does by doing some coding, then some thinking. The only limitation on prototyping is that it's difficult to communicate what is being accomplished in the middle of the process, because you'll make something that looks negligent or incomplete - it isn't trying to answer all the concerns yet(that's what you do in production code).