I'll be interested in any replies should you get any (!) as I am considering a Puck purchase. I'm trying to convince myself that my 1600 bus will be 'man enough' for the job
I have asked the question about being charged double with a campervan and an Eriba on some caravan forums. The concensus from them seems to be (generally) that many sites are not bothered. Those that are appear to send a staff member to your plot to see if you are actually sleeping in both vans. The answer is, obviously, not!
They also told me that in Europe they are not bothered at all. They see the campervan as a tow car.
A Puck is about the same size as an awning and they don't charge double for them?!