USB PS3 controllers on BC PS2 games.

[chipsgravy]

I have an original 60GB JPN PS3 with full PS2 backwards compatibility. However I can't seem to get any USB PS3 controllers to work on PS2 games. The Internet seems to suggest I can perform some sort of switch once the game has booted. But I can't get it to work. Does this only work on the UK models that use emulation for PS2 games? I have a lovely new fighting commander 4 that I would like to use on Last Bronx.