The entire structure is very solid (touch wood). Since the roof rack was made a hardtop has been put on and we just modified the height of the rack to place on the hardtop and I was again impressed with how solid it sits (touch wood again).
Its not really a difficult or challenging fabrication, if you can find someone with experience they can probably do it quite quickly.
BTW: If I was to do it again, the some things I would perhaps bring the overall design (specially the top rail) slightly closer to the rack on the Jeep Dakar Concept (below). The mounting points and the basics would however stay the same.