You would have to take it apart and put it back together again, the sections don't come apart with quick release levers or anything like that. I've just kept mine at 64in. so I don't know. I think it would be a fairly quick job with a ratchet wrench. All the bolts are the same size.

I like the narrow one because I have to go between bollards such as these.

Also for splitting lanes, but I would never do that, if it happened it was not on purpose. The fenders will support weight, I think they say 200lbs? if I recall correctly, so you can carry loads wider than the trailer. It's tricky though to balance loads on the curved fenders. I prefer to put something on the bed to make a platform above the fenders, then put the wide stuff on top of that. For instance, these boxes, the second row is wider than the trailer bed. Build up and out!