We've had one week long trip to the beach and two weekend trips to the lake so far. yes, There was three of us at the beach. I don't think a 7x12 would have really added much to it being a three person trip. it may have given us a few more inches of room sleeping long ways across the entire space. I've pulled 7 wide open style trailers. Most campgrounds that we go to have very narrow roads. many with curbs. A 7 foot wide would be very difficult to back into some of these cramped campsites that you find sometimes at lake campgrounds.
I don't think a 7x12 would really assist in a 4 person camper unless they were kids. Perhaps with a bunk bed setup. I dunno. We're way past the taking of kids time frame.
And we have one coming up in couple weeks where there will be a total of 4. ( my son and his gal ). When son and his gal come, I plan to use a cabin tent next to the camper.
I think the 6x12 works for me and what we do and my cabinet setup.
Saturday I purchased Etrack from the Northern Tool store to begin redoing my camper bed. Wall to wall bed will enhance a three person sleeping area.
I'm going to make it sorta like Chester's bed/couch
http://www.tnttt.com/viewtopic.php?t=43306. With the ability to convert to a couch during the day.