The Norfolk Wherry has a weight of 17 tonnes and a load limit of 25, but the Small River (Navigable) has a max weight of 40 tonnes. 17+25 = 42 which is greater than 40... is it intended that the Wherry, which is the smallest ship in the game, not be able to sail down the Small River? Perhaps the Small River should have a max weight of 45 or 50?