I just point out at the moment they tell me where to stand that I will go where I need to surely see my belongings, in a friendly, but concerned tone. If they resist, I remind them that is there policy and are welcome to get me the supervisor! That is usually with a firm tone. If they block my view or someone else does, I move so I can see the end of the belt, usually stepping to the side a little, if I have to. Even if it bothers them. I don't get upset. I try to appear what think is friendly, but firm about my rights, and their procedure.