Looked at the website and their trailers a few years ago. I like the fact that they use essentially a truss as the drawbar design instead of "beams". Doing the 3D frame means that the framing for the entire trailer can be lighter. Very innovative I thought. Also thought they could change it to 2 struts from the hitch up to each corner to really make it structurally efficient but it reduces what you can carry on the drawbar.
You'll have to get the RTT out of the way regardless to get into the box. Maybe making a lightweight hinged frame for it to sit on that sits just over the lids when closed, and then when the lids are open the RTT keeps your belongings covered and dry.