Simple Planes is a great game, however it's accuracy in game physics and fluid dynamics isn't the best. Shippy456 states, "Due to my knowledge of very basic physics and fluid dynamics, I have become somewhat concerned about Simple Plane's physics and and it's drag model." WNP78 also describes, "Simple Plane's physics are definitely not as realistic as can be. They are pre-computed for each part at the start of the game and not updated if the craft's structure is changed. Parts which have no drag, when moved into airflow, will continue to have no drag. SimpleRockets2's drag model is more real-time, but at the end of the day, with all these things, it's about striking a reasonable balance between realism and not lagging out everyone's device." As you can see from these statements, I'm not the only one who is complaining about Simple Plane's current drag model. So, let's fix this! If you want an update on Simple Plane's physics, let's start voting! Thank you for your support!
I'm a bit unsure about the statement "not updated if the craft's structure is changed". We do know that variable wings like the Hellkesenka does change the characteristics in-flight, and there's a Blackburn Buccaneer replica that uses real-world airbrakes (which expands its tailcone) and it seems to work (never tried myself though, and I can't at the moment because SP.com is down).
Though yes perhaps it could do some adjustments like not requiring super big stablizers. I tried making a Hs P. 75 and found out that historically correct vertical stablizers are far from enough, and had to overlap two of them to barely get a flyable plane...