Apologies for the thread necro. Posting info that could be useful to people googling in the future.
USA version 1.1 of Majora's Mask 3DS save files
Checksum is CRC16 located at offset x1A88
To properly calculate a new checksum the old one need to be replaced with 0D 44, calculated and then...
sometimes to the point of thanking me for my quick actions etc against spam and other stuff, but yea...its either they come to respect me or outright hate me