Tested with the Valkyrie and one passenger module, the capacity of the craft does not raise to 12 as it should, instead staying at 8.
The passenger module should add four passengers per module
Whoops, I screwed up in a previous commit. Will fix ASAP
This still appears bugged under 0.1-83.
Now any number of agents can be added to a craft, regardless of number of passenger modules!
For example i can currently fit all 15 of my agents in the Valkyrie with no extra modules.
Passengers are listed as 15/12! :D

Whoops! It will be fixed.
Issue fixed by @redv
Closing
Most helpful comment
Whoops, I screwed up in a previous commit. Will fix ASAP