Greetings,
I noticed this thread today and thought i'd share what my wife and i've done for a sleep system
in our van-conversion...which we will also include in our trailer build.
Here is an image from my van build page on the Froli Sleep System i ordered/installed.

and the completed bed with two 2" gel cell mattress toppers from Costco:

The FSS home page is here:
frolisleepsystems.com. We ordered the full size kit. I think the weight of the parts is less than 8 pounds. Then i mounted it on an appropriately sized marine ply platform. Placed the foam on top and it's ready to sleep on. As for comfort? The morning after my wife and i woke up on our stick & brick home's sealy pillow top after spending 10 nights on the Froli in the Van after it's maiden voyage she asked when i was going to order a Froli to replace our home's mattress... the Froli is THAT comfortable!!! and supper light. A perfect combo for an RV. The only downside is my wife and i find ourselves snuggling into the late hours of the morning. The upside? We save on breakfast food cuz it's brunch time

Happy Trails,
Thom