My trailer's size was dictated by the three main features I wanted...
1. The ability to carry a three man roof top tent
2. I wanted it to look like a 1/4 ton army trailer, but be scaled up to match the size of my jeep. (An LJ dwarfs the Willys MB)
3. I wanted to be able to mount a fridge/ kitchen on a slide that was accessible with the lid closed & tent setup
I ended up with a frame that is 44" wide and roughly 130" long (counting the tongue). Where it meets the frame the body is 44"x70", and at the lid it is 60"x79".