Number and size of busses

[Ticostar]

Hello everyone,
I have an issue with GSX and MSFS. Every time I start boarding (e.g. 155 PAX) GSX sends 1 big bus and 4 small busses. The small busses carry around 20 Pax whereas the big one carries 90 Pax. How comes that GSX chooses these busses instead of 2 big busses instead? Is there an option to choose the size of busses that should arrive?
Any help is appreciated. Thank you!

[virtuali]

The problem doesn't normally happen, if you follow the boarding procedure correctly, meaning the airplane payload is not changing during the boarding process.

If the airplane has a custom method to set the payload, set it before you call GSX Boarding or after, not in the meantime.