if the airplane is not recognized by GSX, you can use or create an intelliscene file in your aircraft folder (maybe modify one that someone might have made for it), and if you remove a door, GSX will obey and not enable something (like stairs, for example).
If the airplane is recognized by GSX, the intelliscene file will not be read BUT, you can (if you really want, but it's not really suggested) override the GSX internal database and force it to use your intelliscene file, and add the following lines to it:
[couatl]
priority = 3
This will force GSX to use the intelliscene file in the airplane main folder, instead of the internal data, even if the airplane is supported natively by GSX. However, by doing so, you'll lose any additional features that GSX has for some airplanes, like custom doors commands and detection of ground connection so, it's not really recommended.
