tho I still don't recommend using another save, if your intent is to go online. I'm pretty sure saves have a "gamesync"-esque value, that presently the offset isn't known.
(LGPE saves had such a value too, and it wasn't found until pretty late in it's cycle)
This value is used by the servers to tell saves apart, as it is very unlikely to have legitimately stumble on 2 saves with the same OT, TID, SID and gamesync value.
Anyhow, given the offset of that value is unknown, as a result, you can't modify away that value.
(tho, that value would be 0 on saves that never ever went online, including receiving Mystery Gifts, so maybe you could use those)