you could make the actual box of the trailer 5' wide and use the extra width for some side decks (place for the dogs to sleep porta poti, etc.) measure the width of your TV. I wouldn't want a tear any wider than my TV or I would have to use towing mirrors to pull it. Plenty of serious off road campers have a side deck that flares out to the width of the fender to protect it, it would also give you a place to sit out side, or a place to strap on bikes, water jugs etc.
My td is one inch less than a "real" queen mattress inside, full length bed, and 4' high from the floor to the top of the roof. Right now with no inner roof I can kneel on the bed while changing. I'm 5' 10" tall, my 5' 2" wife has enough room to do her Pilates inside, which is how she looks so good after 4 kids.