I don't think anybody can make a plane on paper that is optimized and ready to produce without building a plane or three and burning some fuel. But preliminary analysis cuts out perhaps 80% of the cut n' try by getting you in the ballpark before you ever start cutting wood. Best of all, it can quickly eliminate all those "cool and sexy" ideas that we often fall in love with but are DOA by exposing them to Newtons world. Frankly, I think you need a lot of both.