Paddysaab,
I guess there could be a couple of reasons. Have you checked the ride height ? I think only the Aero was lower. I though 40mm but I seem to remember some discussion on another site that it might just be 25mm. Next is the tyre profile. 195/65 on a 15 inch rim ( 205/60 is near as dammit the same ). If these are both OK then I would suspect that the shock absorbers are getting a bit soft, allowing more movement in the CD.
There is very little difference in weight between all the varients. A couple of suitcases and a Granny in the back more than cover any varaition.
Paul @ Kippen.