Have you ever heard the old axiom "you never want to know how the sausage gets made"? How models get made is mysterious for many of us, and can lead to criticism of a models accuracy. Sometimes, that leads to eating sausage made of crow. How did Monogram's designers get their data for the SR-71? You may not believe it.
This is partial text from the full article (usually with photos) at https://aeroscale.net/news/model-industry-history-monogram-s-sr-71-and-their-5800-series-aircraft-kits