Can i copy/paste a "sources" file or to another site (all things being equal)

[Nodaz]

I have three instances of SMF running, all three were at 2.0.14 and wouldn't update correctly, lots of mods installed and uninstalled.
I have successfully refreshed  the files on all three one sites using the  large upgrade package, proceeded to updated to 2.0.17 and installed the same two mods that didn't require any code modification.
The third mod i would like to use requires 4 or 5 fairly large edits to a file in the sources folder.

Presume  that all three sites are updated exactly the same, and will run the same three mods.

If edit the file on one of the sites and it is working properly, can i then copy and transfer that same file to the the second and third site to not have to manually edit each one?
I plan on installing the mod first on each site, editing the file on site one, make sure everything is working correctly and then copy paste the file to site B and C

[Kindred]

Potentially,  yes, that should work