I did talk to the
Parkliner expert in the Facebook group. This was his response.
The 4 screws on top of the floor there are at least two under the floor in the rear holding the shell in place, next the front screws are under the shower pan, so the whole shower will have to come out, next there are screws into the entrance frame behind the lowered.door trim pieces that would need to be removed to access those but there are screws in the front of those going into the wood door frame, all of those are body worked in and will have to be ground out.
In other words, the screws are hidden between the shells and impossible to get too.
I have a plan to fix the frame without removing the body.