Yes, the cylinder slides through the pivoting tube. You can unbolt it and pull it out to service it.
Yes, I have a back wall. I have seen them cut and sectioned like you said, and I haves also seen them where they just drill out the spot welds and cut off the excess at the bottom. I will probably do the first one.
While the body is getting painted... I have a side project in the garage for a friend. 2008 Impala, 2 pump 4 dump, 3 optimas, & a street charger.
getting started today, should have it done sat or sun.