Is the center hole a square, diamond or a octagon? If you rotated it so it looks like a diamond then it should be restricting the move in the diagonals.
The restrictor plates can be a pain. If its something you plan on changing often then you may want to look into a automatic switching setup like the
Servo Stick or maybe a
Mag Stick or Mag Stick Plus These can be changed from 4-8 with a flip of a switch. the Mag Stick Plus can be changed simply by pulling up on the control stick and twisting it. be warned that the throws on the Mag stick are very short.
The servo stick is cool because you can program it to switch automatically based on what game you are playing.
There might be other options but those are the two that I have personally used.