Northsea 27.
I can't afford one but maybe you can. I saw one on a triple axle
trailer pulled by a 60's International truck (maybe 450ci). They made
it with two couples from VanCan to San Carlos, Mex no problems. It has
an after cabin so there's some privacy of sorts.
I am puzzling this one out too. I bought a 5000 lb boat and after two
years have given up finding a cheap used trailer to modify. I can get
a double axle trailer built for about $3000 and a used tow vehicle of
unknown reliability for about the same price.