I built it primarily with the Generic Benroy Plans with a few modifications.
It has 2000# leaf springs, shocks, 3500# axle with brakes. There is a 2" .095 wall square tube frame with 2"X3" .125 wall tongue with 6 crossmembers. A LockNRoll hitch provides flexibility offroad. With a frame height of about 22", it sits level with my lifted Tacoma and should provide plenty of clearance for offroad excursions.
The siding and roof are anodized aluminum from SoCal Teardrops with diamondplate stoneguard in the front (making up the remainder that a 12' foot sheet won't cover). The doors are from Little Guy Trailers in Ohio.
All of the lighting (not the trailer lights) is LED for low power usage. There is a Fantastic vent in the ceiling.
I couldn't have done it without the help and ideas from everyone here.
A photo from the offroad testing last Sunday.