However, when I place the PS2 on its side, no matter what I do I cannot get Mobile lightforce 2 in this so called "Tate" mode.

I doubt the guys at Best buy will even know what TATE mode is. I am not confident it is actually the stand, because if I turn the PS2 in any direction it does not force the game into TATE mode.
I'm sure I will figure it out in a couple of days
