Hello there...
I think having a light weight version of these ships is a quite unrealistic thing! Only time where they are light weight is when they sail back after unloading their cargo! but they have to reach the harbor loaded!
Thats why they build so long docks which reach up to the deeper waters for those ships to moor!
And/Or they dig out the riverbed!
So in my opinion its just realistic that you get problems with finding a mooring place for these large vessels!
And for me its ok because ShipSim is an simulation and simulations usually follow real life rules!
anyway...
Cheers...Jonny