Just searching the net , see a LOT of metal corner brackets ... thinking it would be easy to get a dozen or so and have at it .. Thinking you could overhang the front of the trailer in the same way (longer) if well braced...
Ya’ Know , the more we reinforce/Brace/ bolt/weld/fix this to the trailer box , the more the idea of a removable cabin quickly fades from sight...

Bolted and braced as we envision , I can only imagine someone of British descent having the ability to take it apart and re assemble it ...
