Just created my Skylon spaceplane with realistic dimensions, 15 sections at 5 (I assume metres) each + nose / tail caps is approx. 80m. When I upload it, it's reported as 39.3m, which is about right for half the length. If the measure is feet, it's still wrong as it comes out at 129ft.

https://www.simpleplanes.com/a/FZ72bl/Skylon-D1