This is why I wanted to secure the rpa file first (Yes I know its impossible to do 100%).
It's not that it's impossible to do it at 100%, it's impossible to do it, point.
More or less ten times someone tried to do this with a game available here, not once it needed us (the community) more than an hour to release an updated version of unrpa that worked with those "protected" rpa files. As for the rpyc files, I even released a script that automatically "unprotect" them.
I did find a way to secure my files in the end so its all good now.
I'm pretty sure that you didn't. But even if you had succeeded, it would have changed absolutely nothing. Changing a screen
without access to the source code, including the game main menu, is a piece of cake, and replacing an image don't need that the said image was firstly erased from the rpa file where it's stored.
Therefore, whatever how deep in a stronghold your files can be locked, the level of protection will still be 0. It's something that you have to accept, and therefore being tricky will be more effective than passing hours trying to achieve what can't be done (securing your files).