I've killed NUMEROUS non-business projects by trying to design everything up front. The ones that have succeeded started small, adding objects and features organically as needed. So just make your database/config settings easy enough to swap out later, and build iteration 1 first with the rough edges. It's something I find really hard to do... I want to break out the notepad and start creating lots of objects, but that (IMHO) is a quick way to end a project.