I thought I would put this here because it is germane to the task but differs in source>destination.
I have a V2 Mega Everdrive runing 3.x and a pro running 4.11
Both work fine but I've noticed that the SNAP folder .sav files in the v2 are not compatible or at least do not load on the pro cartridge.
(I copied the files to a folder inside MEGA called "legacy" rather than swap SD cards as that would also swap the OS)
Are these users in the same boat as the MiSTer converting users?