Yes I added a large box on my goose neck when I had a top deck,,,when over weight Wyoming and a couple other states will give you a hard time,,I welded mine on,, Wyoming will allow only about 600 lbs dunnage even if you can permit the extra weight,,I hauled a few new linkbelt 90ton truck cranes and Wyoming would allow the cranes stabilizer pads or the fly boom,,I would suggest you mount it permanent
This was my set up. I'm not pulling this trailer anymore. Just a Job box like you would find on any construction site. Chained down with a couple binders. No issues.