Thanks again damysteryman, but something got wrong...
I have installed Hackmii / Bootmii (as IOS only) / HB Channel, and made a NAND backup.
But when I try to uninstall the oldCORP with the cIOSCORP 3.5 Uninstaller I get an error:
"cIOS 249 not found -> You need IOS16-64-v257-prod.wad and...