Welcome to the forum. I see no responses to you so far and mine may be of no value either since I don’t know your coach details at all. Sounds like you are missing some more scres holding down the metal access covers. Attaching a link to another Forum that might help assuming older Astorias are built similarly to yours (although this link has minimal content).
https://www.irv2.com/forums/f120/ast...ss-241221.html
The other thing would be to contact Thor and ask them for construction details for top engine access assuming you have not already done that. Sometimes if you post a picture (JPG) on your post it might give members a better idea of your situation. If nothing else, it gets your post to the top again at least. Good luck.