For more detail on how effective Skunkworks was, read Kelly Johnson's book. It was recommended to me by a buddy at JPL and it's a wonderful view into how they did things on time and below budget on projects like the SR71.
I love the problem solving stories. My favorite is the one about transporting the prototype from Washington to Nevada on a very wide trailer- which involved sawing signposts apart and bribing a bus driver...
Not an affiliate link: https://www.amazon.com/Kelly-More-Than-Share-All/dp/08747449...