"They seem to all framed - looks like 2 x 2 - and sheathed in plywood. I would imagine you could build them with 1/4" ply glued to both sides of foam - at least 1" and maybe for 6+ feet spans, 1 1/2". That would give you a 2" thick wall. Cabinets or closets would add a lot of support - basically functioning like a bulkhead. I'd work real hard to not have any flat roof profile for the stiffness of curve provides. And I would always add solid wood at the top of wall for the wall roof joint - even if just a 1 1/2" wide strip at perimeter - but you might find other ways of doing it." Agreed; I was looking for something like the TAB320/320CS or the Bushwaker 15FK. I had planned to modify the shape just enough to get a continuous arch and no flat spots but I was thinking more for water and snow shedding, but yeah extra strength makes a good additional bonus I didn't think of. Too bad there wasn't plans for a more teardrop shaped standup trailer.
"Look at the
https://bowlus.com/ trailers for using the body shape for structure. A lot of strength in the curved plan and section. Or just buy it for a $ 1/4 m.

" - Quarter Mill? Chump change
"I did google images for the names of those plans and found nothing contemporary - just the vintage photos." Sma here, although I did find some bottom up rebuilds where the end result basically only reused the siding, badges, and appliances. Also found some builds around the size I am thinking but they were very square and blocky and I want something more rounded and tapered off.
"The closest here may be woodbutcher's standrop - but still not as long as you suggest.
viewtopic.php?f=50&t=68091&hilit=standrop Pretty light weight for the size, and a work of very fine craftsmanship." As long as it has a double to queen bed, a wet bath and some sort of kitchen, internal or external, then it would be fine. I think this is a great thread with lots of lessons to be had but the design again is really blocky.
"I think it will be challenge to keep under 3000 pounds loaded. I don't recall your goal for max weight. Googling " weight of 16' travle trailer" returned "On an average a 16 feet length travel trailer will have a unloaded weight of around 2200 lbs to around 3400 lbs."" The bushwaker is 1900lbs and the Tab's are around 2200lbs neither has an axel rating of 3500# so even if loaded to the absolute max they are both under what I can tow. Now I haven't towed too much and when I did my boss at the time determined what towed what and how much was loaded. That said my book says 5000# max, 4500# with 4 passengers and many guys I know with smaller SUV's like CRV's RAV4's and older Outbacks tow 3500#ish all the time with no issues so I think I am safe at limiting myself to 3500#. That said part of the reason why I was looking to build my own was to put a heavier axel on it because, as a family of 4, we tend to hike and mountain bike and fish and hopefully hunt. So it will have to have the capacity to also carry the gear of 4 be it 4 mountain bikes or 3 canoes\kayaks\paddle boards whatever depending on the plan and destination.
My mother has a 1970's Bell M-1700 that has front dinette, rear bed, bunk above that, furnace, and wetbath she uses as a bunk house and it is listed at 2700#; in all I don't think it is unreasonable to expect a package weight of under 3500# in a trailer under 16'. Then again that is speculating, I really don't know for sure. If I can find a vintage trailer to rebuild I would rather rebuild and upgrade the axel than build something.
"Maybe "Teardrops n Tiny Travel Trailers" just doesn't fit what you are looking for." Well how small is small? a 22' camper is small compared to a 38' gooseneck trailer; the site features plans for trailers bigger than what I would ever want so I guess it is all interpretation.