That's a great idea Hairs. Guess we have some drinking do! Would you normally use a spreader bar across the center?
When we had our trailer tent, we let the tarp rest on top of the campers canvas & frame work, I had replaced all the internal poles and spreaders with stronger ones than the ones supplied, also added spreaders to that frame work as well.
The tarp just laid over the top with poles and ropes.
Have a look here,
Our Previous camperIt may give you some ideas.
Camped till Sunday mate. Guess we will probly be packing up in the rain too.....The floor bottom is going to be a mess.
We used 90% shadecloth under the flooring as well as in the annex area, stopped a lot of muck sticking to the vinyl.
Hope it works for you.