A few years ago (2011) we decided we needed more room for hauling everything to craft shows. Here is a picture story of what we came up with. After three years of use we are now considering how to up-grade it a little more, although it has worked fairly well as is.
This is the trailer we purchased.
Then we stripped it to the floor.
The walls were painted, then added, leaving an opening for the side door.
On the other side you can see how we staggered the side walls, trying to make the most efficient use of our 4x8 sheets.
From the back it looks like lots of room!
And doesn't look like it should overwhelm my hauler (it hasn't)
With side door, flat fenders (handy for setting things on) and new tires it was finally road ready.
We secured the back doors with a slat that slid through the handles, later replaced by a piece of rebar for added strength and easier sliding.
Loaded for a show, you can see we also placed a 4x2' table to make sure nothing could slide backwards during a hilly drive.
This last picture gives a better view of our roof supports, and the amount of light that the light colored roof does let in.