You that are lucky enough to be able to put rads in the back of your vans will find another benefit.
You will have a lot less residual moisture/condensation in the van. Thats what can do a lot of damage.
My van failed its MOT last week on rust , OK its a transit and thats what they do, but he said as I have all that water and chemicals in the van and the condensation is adding to the problem.
I have an eberspacher that keeps it warm but I still have condensation probs. I would be inclined to keep the rad on low when its not that cold, it must keep the warmth up to a level whereby the condensation doesnt start and all that water that gets slopped around in there dries out.
Murky