That's one more thing to clean up !! 
I did inspect the mounts and firewall. The firewall will flex and it does with the side planking to a degree before the mounts will move. Probably the lack of any support across the top I would think. Only thing that could be done would be to add a second firewall as there's no room to put anything in to tie the planking together at the top.  It will have to be OK as-is.