Keyslots has been managed in ncchflag[3].
If you set ncchflag[3] to 0x00, Keyslots 0x2C is used.
It should be same as SeedCrypto.
I make a cryptofix .3ds rom worked in GW n3ds 9.5.
also decrypted rom worked in citra.
Edit: I tested converted .CIA worked in GW n3ds 9.5. so, more accurate that...