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I've seen this type of material used before to assemble fixtures for optical instrumentation.
For a general purpose roof rack on the Discovery it is not an appropriate material because it is too bulky with needless rigidity. The load bearing capacity of the Discovery's roof is too little to make any use of it, especially if you are just mounting on the gutters. It could be good if you were using a single piece of it to mount a single piece of equipment or instrument.
A similar material is simply t-slotted extruded aluminum flats. Find my earlier post on roof racks and see the photos of the Hannibal Safari roof rack that uses these t-slotted slats. They are essentially the same but with only one t-slot surface instead of four.