Their is no difference between a curtain sider and a boxed trailor being on a loading bay at a distribution centre, they get tipped in the same way, the material the walls are made of have no relevance to the point you made. Curtain siders do have back doors you know that open the same as a boxed trailor

Companies like Royal Mail use boxed trailors because obviously mail needs to be kept dry, boxed trailors are generally specialised trailors for specialised work.

Remember were talking Stobart here, Stobart is mainly general haulage, they are geared up for that work which is why their general haulage fleet run mainly with curtain sided trailors. They have specialised sides of the business like biomass and fridges etc.