OK, I'm going to give two sets of measurements. The first is the rear dinette/bed I built for my CCV home-brew conversion. I still have the dinette out of that van since I sold it with the bed only I that replaced the dinette with. The second is the mid-ship dinette/bed in my current SMB.
CCV rear dinette/bed: (more of a 1.5 than a bed for two, I would recommend making it 48" wide at least for two people)
Each base/side is 20" deep x 36" long (or width of bed) x 14" high. On top of this I put 3" standard foam which was good for a bed or seat. I could barely sit back there and eat a meal, only did it once or twice. My head was basically scraping the ceiling, but I'm 6'2"
SMB midship dinette/bed:
Each base/side is 25" deep x 48" long (or width of bed) x 11.5" high, which gives you a 48x68" bed with a floor space of 18" in the center of the dinette. The bottom cushions on the SMB are 20x48" and the backrests are 12x48".
It is important to remember, however, that SMB uses a metal frame where my home-brew was wood, so with the SMB structure the backrests are at a comfortable angle as they rest on the frame and on my home build the backrests were basically sitting straight up since they were just leaning on the sidewalls. 3" foam on the SMB as far as I can tell. It's very comfortable.
Hope that helps, here are some pics
Linear Mode
