One car review I read (I think on drive.com.au) said that the 05 model had stiffer suspension settings -- and that there was far less body roll as a result.
I'm not surprised at the line about not officially putting on 17s on older models which have different mechanicals: Mitsubishi used to have a similar line about Magnas until the later models where the suspension mechanicals were changed. The official line was something about "under extreme conditions" certain components could touch. To certain extent, you can understand where they're coming from because they have to warranty the vehicle...