I don't know how to change the controller plugin but the default one is frustratingly unintuitive when trying to configure the analog stick. You don't set each direction or axis so the directions are all messed up when I try using it.
..what? If you're using lilypad,there is a button for each axis direction. It doesn't get any simpler than that.
SSXPSX Pad Pressure Mod 1.7.1 is what it says when I mouse over the controller plugin option. I put lilypad in the plugin folder and I don't know how to select it. In the controller plugin options the SSXPSX thing is greyed out and there is nothing under it.
Oh and I get an option for every direction but only once and I assumed it was for the D-pad and that the part labelled Analog was for the stick.
Are you using PCSX2 1.0.0? Because lilypad is included, you do not need to download it separately.