I'm no expert on this by any stretch of the imagination, however I do remember reading something like this:
PAL is 625 lines and NTSC is 525 lines (horizontal resolution).
Due to this simple fact, NTSC games will appear smaller on PAL TVs and vice versa. Unless the game natively supports some form of centering options, there's little that you can do about it.
I live in the USA and have kinda witnessed this myself. I have several PAL games that have been patched to NTSC. What I see is obviously the reverse: the games 'goop' off the screen. Luckily, most have a centering option to correct this as best as possible.
One more thing, I do remember reading that certain M-clone chips (Elvis, etc) can adjust NTSC games for PAL automatically, however this is the only way I know of to fix it. For more info, check out the modchip comparison chart at PS2Covers:
http://www.ps2covers.nu/comparison.asp
Hope this helps
Tril