NarrowGauge bridge maximum allowed weight balancing

Hi. I am playing the extended version of the nightly pakset (without any addon) with simutrans extended and i find that narrow gauge bridge (which there is one option only) is too limiting compared to standard gauge bridges.
Just using a 3-tiles long NG train with EMPTY coal wagons is enough to go over the weight limit. Not sure if this is an issue with overall balancing of the pakset values or an specific issue with the pakset in extended and having non-human cargo being able to be loaded over the limit (overcrowded capacity in a coal wagon for example) unless this behaviour is intended.