Here is a thread detailing the reconstruction of a Camelot, which should have the same roof construction. The OP also has posed Youtube videos on the reconstruction that might help, you'll just have to look for links.
If you look at post #586 it shows how the roof is constructed and the layers required to form the curved roof to support it.
If your body shop left some of this out it won't support the fiberglass top.
The roof ladder is supported by pieces of wood that are embedded into the fiberglass when the cap is made, they basically take wood during constuction, epoxy it to the underside and spray woven fiberglass and layers of epoxy over it. Once in place it doesn't move or rot if fully encapsulated. If they left these out there will be nothing to support the attachment points for the ladder.