When I got home later in the day, I got the floors of the sunboxes up into position. They are lightly tacked in, just to ensure everything is plumb and square (they are....) and I can rebolt them later with more washers etc. I have only one detail to improvise, the rear part of the floor where it meets the opening bottom louvre. This needs a custom flashing section which I will have to make by bending sheet aluminium.
I have tried to do all the components on the ground so that the whole thing is assemblable-disassemblable, and made as accurately as possible, in conditions where I can lay everything out. However, there is still a lot of customisation because it is fitting to existing metal brackets and rails and polycarbonate sidewalls. So if I was starting again with a 4 square meter system, I would do the fixing details with less complexity although the exterior profile that they have now is as perfect as I can make it.