I can't help but think the factory fitted brackets should be pretty strong in a van,as they are designed to lash down heavy loads,I will have a good look and a test when i get the van.Like you say,Vans carry all sorts of heavy loads around,thats what they are designed for,I was in one last week with a ton of sand,half a dozen bags of cement,a cement mixer and loads of tools,none secured down,only a bulk head for protection,Insurance companies do not ask any questions about this!! The van I am potentially buying was used by Hotpoint to carry washing machines etc around,Now they must weigh a fair bit,and I bet they were not tied down!!