The problem with this Starcraft is that it's a little over 1/2" to cover the rivets. I think they managed to keep them closer to the edge on later ones.
I'm looking for some RV awning rail for another project and am now wondering if I could use some of that. Some of that is 1 1/2" high so that should cover my channel but I'll still need some 5/8" aluminum angle in the 1/16" thickness under it. Another possibility would be to use a couple awning rails, one on top and another over the open channel. Something could be slid in between the 2 channels. Just some more thoughts.