My wife slept on our Air Down Gear Up platform this weekend and said it was great.
We have an almost identical set up. I am 6'4" and my wife is a about 5'8". We fit perfect in the back no complaints. I spread out a lot when I sleep. Also it is the only time we use the entertainment system. But we only use it when we are in a hurry when traveling and the weather is really bad. We generally use the ARB awning and tent. It's a lot of space but it takes about 10 minutes to set up and 15 to break down. We keep the 2 person 4 season tent in the back all the time. It's almost never used for truck camping but we found if we are staying in the same place for a few days it's like a travel shed to store things like bedding, clothing or just stuff. It gets filled up quick with group trips.
To the OP. If your in a pinch and need to sleep and don't have the platform bed set up. Remove the headrest from the front seat you choose to sleep in. Move the second row seats as far back as you can. Next recline the front seat all the way back and move the entire seat back until it touches the 2nd row. It becomes a sofa. It's not a perfect flat but close. I do not fit across the back seat but this works for a tall big guy.