Why does my screen roll? PAL on a NTSC

[Skypig]

I Have a new PSOne with a Mod chip and it seems to play NTSC burnt discs with no trouble, but when i burn a PAL and patch for the area code, it first reads the right area code now, but the screen rolls like the vertical hold is messed up.

Is there another patch that i need to use to get it to look right on a NTSC machine? Seems to be some info. at Gamecopy World but i'm not sure what i'm looking for.

Thx ,