How to mod a flatpak game (openspades)

I have tried to dig around to find the answer to this but have been unable to.

I want to create a semi-persistent modification (survives until next update/uninstall) to a game directory for openspades to change the sights. when compiled the files would be found @ /usr/local/share/games/openspades/Resources however I have no clue where the files would be with the flatpak install.

Any help would be appreciated. (And apologies if this is the wrong place to ask for help.)