We've attempted to enjoy the double, the sofa pull out from the front, but ended up building two twins for the mid coach 72 31 foot international. many times I wish to have a double plus, but one of us will have the curbside of the coach to face due to all of the vents and water lines on that side. In a recent Extreme RV show, the showed a bed, similar to a futon, that electrically went into sofa mode and then at night with a touch of a button went into a queen size bed. I wondered, can this be placed perpendicular to the mid coach to work? Still researching.
We ended up making mid coach twins, bought the mattresses to fit from Bradd and Hall 32"x76" memory top (12" total depth) and to be honest, they work fine and we sleep very well. At the expense of trading up, or continuing to spend hundreds if not thousands of dollars to refine, this is a very good compromise. With the open floor to go forward and aft of the LY life is good. There is a comeback for twins it seems as after a great day of being with the family, sleep is a good thing.
I've attached a few photos to give you an idea of how it will look with two 32" wide mattresses. they are grainy shots, but I think you'll get the concept.
Only thing we did not due was build the bed platforms to lift with gas pistons so you can use the storage. Plan on fixing that this winter. Also recommend using marine plywood for the platform tops.
Good luck and its only money!