I designed a similar size for my neighbors to construct for me.
SilverLite horse trailer manufacturer in Springfield Oregon.
Unfortunately, they were another casualty of the 2008 bankers contraction.
This's a shame.
We were set to start construction on an aluminum goose-neck tandem dually, GVWR of 24,000#.
We designed, they engineered, massive tanks for drinking water, and transfer fuel tanks.
And a slide-out BBQ.