[bballer]

I find that as long as you start with the DB schema and core interfaces (system level rather than code level) and then move to framing out the general pillars of the code that you often will get 80-90% right. Refactoring will be a plenty but that is true in every project no matter the upfront planning. Just don't miss any edge cases which rewire your schema and you generally can keep a good pace on forward progress. Also it's generally true that the larger (see more complicated) the problem the more planning one should generally do.