Bonnie & Claude : From the sound of it, you like the idea of having the stern dinette converted to a bed all of the time.
This is exactly how we have set up our Trillium
1500 as well...but of course, for resale purposes, we ordered the stern dinette & forward dinette version.
Anyway, when we were first setting up the trailer, we put a double mattress on top of the lowered stern dinette rather than using the seat cushions that would threaten to destroy our backs.
The obvious problem with this was that it was a pain in the a** to attempt to get anything out of the storage compartments under the seats of the stern dinette.
I felt there had to be a better way...and there was !!!
Thankfully, we have a mattress manufacturing company here in Windsor (Monarch Mattress) & they are used to doing custom jobs for boats & Rv's.
When I took this problem to them, they suggested to have a thick foam mattress built in three sections & joined by a "tufted top" so that the outer sections could be folded over to allow access to the storage beneath.
We had this built & have been very pleased with both the mattress & the access it allows.