I have a comment on one little aspect of the cage... Take it or leave it, it's just a comment...
If you were to "apply downward force" to that top bar (like rolling on your lid, for example... not that it will happen, purely hypothetical

) that little bend in the rear-most diagonals would give the force a direction to bend those diagonals... and they are going to bend toward the interior of the bed (and your "stuff" in it), while taking out the nice shocks... anyone else see this?
Hate to sound pirate-ish, but more triangulation?
Overall, I really dig this build... great stuff...