I've got a j-stick, and I only use it for 4way games. I mounted mine in 3/4 MDF, so it's about the same height as a Ms Pac joystick without any alteration of the underside of your control panel or need for a mounting plate.
I have to say that the j-stick is great on 4 way games. It allows you to slide from one cardinal direction to the other without doing a wave motion-ie joystick must follow a parabola to move from up to right. (the way it looks like you have to do with the restrictor plate). Although, keep in mind that I have not tried the restrictor plate, I'm just commenting on the way it looks.
The stick also works well in 8 way mode, although I generally don't use it for 8 way games b/c I don't like the fact that the ball top sits so low to the wood control panel. Most 8 way games I play need to be played with a high joystick I can get all my fingers on
hope this helps, and if it doesn't make sense, it's because I've been working on my cab for waaaaayyyyy to long today
wee beastie