While certainly not 'approved' or 'measurable by engineering standards' while helping to assemble a Total Composite box myself and others were debating if 'filling' the hollow section would make them stronger. I took a 2 pound sledge hammer to a spare section and 'beat the living heck out of it' with nothing happening other than the hammer just bouncing off and all of us being quite impressed. I would say not recommended for other than 'spare' sections, but I was very impacted by the results.How are these mounted to the roof? The extrusion pieces on the perimeter of the box are hollow so I assume they are not mounted there, so how does one mount them? Can't find many examples of these on DIY boxes.
They are commonly rivnutted and maybe glued. As @mog mentioned, the extrusions are strong and the job of these rails are to act as branch deflectors and/or a final reminder that you’re about to do something you’ll regret on a tight trail or parking structure.How are these mounted to the roof? The extrusion pieces on the perimeter of the box are hollow so I assume they are not mounted there, so how does one mount them? Can't find many examples of these on DIY boxes.
While certainly not 'approved' or 'measurable by engineering standards' while helping to assemble a Total Composite box myself and others were debating if 'filling' the hollow section would make them stronger. I took a 2 pound sledge hammer to a spare section and 'beat the living heck out of it' with nothing happening other than the hammer just bouncing off and all of us being quite impressed. I would say not recommended for other than 'spare' sections, but I was very impacted by the results.
Are you saying that the extruded rails do a good enough job that I don’t need anything additional?They are commonly rivnutted and maybe glued. As @mog mentioned, the extrusions are strong and the job of these rails are to act as branch deflectors and/or a final reminder that you’re about to do something you’ll regret on a tight trail or parking structure.
It depends on what you need the rails to do. You don’t need the rails at all. IDK if they actually add anything apart from looking cool. I don’t have any on mine.Are you saying that the extruded rails do a good enough job that I don’t need anything additional?

The FRP pultrusions would be prefect as the glue surface. Here is a link to the instructions: total_composites_accessory_bracket_install_guide.pdfYeah, I'm thinking more for protection of the fan and solar panels than anything else. I certainly won't be wheeling my rig, but even the forest service roads can be pretty crowded with trees here in the SouthEastern U.S.
@Victorian do you recommend the panels are glued to the panels themselves, or to the Extrusions?