You mention that you start with a blank piece of paper when you begin the design work. Hi Deborah, No, we don't.
Requirements change or develop over time, based on solutions and problems encountered during design.
YES to both. Yes, but that's inherent to once-off work. Since there is only one shot, we do our best to make it happen. We only build one side of the model, in our case the left side. It's placed in the tunnel with the wing up, as if flying in a 90-degree right bank angle.