Someone on reddit put a 2TB same model Seagate drive in I saw. They just cloned it and then extended the extra space. Bad news was I gather the guid table still thinks it's a 1TB drive so a factory reset would cut it in half lol.
I think there's a way to do it still using the old 360 trick though so factory reset knows it's 2TB but so far 2TB is the largest size that can fit physically and has the table files kicking around to survive a reset.
Guess my plans for an SSD kinda fall flat for the time being lol