Screen adjust for games that don't have the option

Hello everybody!

I'm french and i'm actually trying to "rebuy" all the games i've already got in PAL version, in NTSC (US or JAP).

I finally got my hands on the US version of "Final Fantasy X", but the guys at square forgot to put one very simple option into the game : the screen adjust!

When i launch the game (with hdloader, i don't have a modchip), the screen is not centered, it goes way too much to the top and a little to the left (CRT TV with RGB cable). So what i need to do is correct the offset (X and Y axis) so i can center the image.
I think there might be a way to "patch" the iso i made out of my original, by changing some values with an hex editor, but i really don't know how to do that kind of thing. Also, i don't want to patch the game from NTSC to PAL, since i want to keep 60Hz display.

Can somebody please help me? Thanks.