Road based goods transport suffers (imho) from really high cost for the station infrastructure, especially after the staging inn retires in 1844. At that moment one is forced to use the cargo bay with a capacity of 128, which is an insane capacity considering, that trucks won't hit a capacity of 30 until the 1960ies.
I would suggest that there should be 3 cargo bays of different size available at all ages, the sizes grow over time.
pre 1844: small 20 goods, medium 40 goods, no large, but there is the staging post with 10 of all and the staging inn with 40 of all.
until 1920: small 20 goods, medium 40 goods, large 60 goods
until 1960: small 30 goods, medium 60, large 90 goods
post 1960: small 60 goods, medium 120, large 180 goods
Basically the small bay retires when it becomes to small to hold the load for a single up to date truck. The larger variants should hold at least 2 or 3 truck loads.
I started playing around with blender using the blends from JamesHood to make some cargo bays by adding some cranes to the standard cargo bay to create some that give the impression of a more important/larger station.