Hello dear friends,
Huub , yes it's true these pop-up windows are very awesome but like you write " impact on the total weight of the aircraft and the point of gravity" and created one soft for added the passengers is maybe a big work and a great task.
Only the conceptor of this great addon can explain to us if it's possible or not...
Mathias, a great thank's for your link because there's few minutes I discovered a real treasure with these manuals and handbooks.
Best regards and have a good day, Skull.