I think just on the rack is better:
depending on what you're using the rack for.
Still I had a couple of ideas:
1. slide out on large drawer sliders (prob. bad due to wind)
2. make an access panel that folds up to expose the solar- if you're packed no solar. I was picturing this more with a mesh floor rack.
3. Make an H panel that flips over to expose solar:
You would still have either solar or storage solution and the solar would be protected when not flipped for use.
But again, I don't know what the shadow from 4 or 5 bars across the panel is... I was thinking a mesh floor rack or one like above, not something more open in design.