Maybe this is a stupid question with a straightforward answer, but - why not use ss wire for tensioning the beam ? Or thin rod ? Round section material is best for tension loads, I assume the flat strip setup is used because it "cuts" the waves better than steel rod ?Or maybe adds rigidity in the horizontal plane ? But how large diam. should be enough for the tension there ? 5-7mm ?

I'm asking this because the flat ss strip looks too much extra material to me, for the tensioning purpose.