Allow me to repost my 'teardrop'.
This is Thee Holy Template, distorted, truncated, and reduced to four simple curves. (I stayed up late that night)
Construction would be lifted from the 1952 Silver Streak I used to own. A central tubular spine, C-channel crossmembers tipped with carriage bolts into the deck.
Flip-out step/porch and a Gothic door.
Edit: An example fender:
