Region Unlock PS2 Backwards Compatibility

Hi everyone, I have a CECHA12 PS3 (which is a Japanese region PS3) and it is currently running Evilnat's 4.90 CFW, specifically the [PEX][CEX] variant and I was wondering how I could get my North American NTSC-U PS2 discs to work on it.

I know I could just run back up ISOs through Multiman, but I want to actually use my discs on the PS3.

Any help or clarification would be much appreciated. Thank-you.