the max width and height of the docking slit? Is the "boundingBox" property sufficient for this?
In the case of the old dock model with brick shape, yes. I use only this in ILS
because this is the only way that I found in js.
A more complex way would be if you open every dock models in wings3d to measure the inner sizes of the gates and make an array of dimensions based on the datakey of stations. Note there are non-rectangular inlets in Rock Hermits and Superhubs.
Somewhere we discussed that there is a validator in the core which put a message into the log when a too big NPC made an unsuccessful attempt to launch through a small dock. This part probably use a more accurate code for the size check.