Since everyone's talking about bigger is better. Here is my design for a 6' wide, 12' long 6' tall trailer (from ground). Essentially, it is a rear walk in with a 6' wide couch that folds down into a 6' x 7' bed (King?). The galley is split on the two sides and the hatch is two parts, ala Goose. There is a second hatch that pops up ala Westfalia with a 6' x 4' bunk overhead.
Ubertear!