After the last visit to the Caravan & Camping show I got some more homework to do. We have seen a caravan with a fold down deck. However it was in the front of the van over the A-frame, which is not really an option for us and it was done in a way I would not want to do it for our van.
The deck looked nice and all detail was well thought through, but there were a couple of aspects, which I would want to do differently. First of all it was too heavy with over 100kg added weight and secondly it had not support from underneath. The weight of the deck was hanging on two cables attached at the top of the body. This requires additional strength in the frame and puts stress on the mount points and the integrity of the body.
I use a slide out rail, which supports the deck from underneath. The rails slide out of the main chassis rails and are resting on polyurethane rollers. They are simply pulled out manually until they catch a stop and then the deck is lowered onto these supports. This eliminates any strain on the body of the van. The outer fold down cover creates a roof over the deck at minimal extra weight.
If you want to know more details then please contact me.