I haven't installed this mod yet, so I don't know if in-game values will differ from your descriptions. However, I just wonder whether your table might be wrong.

For fluid wagons, 1 capacity unit corresponds to 2.5 weight units (7500:3000), while for heavy fluid wagons, the ratio is 1 capacity unit to only 1.14 weight units (4000:35000). It's different for cargo wagons: normal cargo wagons have a ratio of 100 weight units per capacity unit (4000:40), heavy cargo wagons a ratio of ca. 106.6 weight units per capacity unit (6400:60).

Is it possible that you got the figures mixed up in the mod description, or is that an error on my part?

Thanks for noticing.
The table with stats for wagons was completely messed up.

You're welcome! :-)

Something else: What makes express wagons go faster than the normal and heavy varieties? I can understand why heavy wagons are heavier: because they have more inventory space. But express and base cargo wagons have both 40 slots. Wouldn't it make sense if express wagons could carry less? IMHO, there should be some price to pay for being able to go faster.

There is no such drawback in RL either.
80s era wagons are heavier and have lower vmax than modern ones, because we now use lighter materials and better optimized boogies.
Maybe I should drastically reduce HP to reflect Express being all about weight reduction and speed.