I have a 2004 Super 9 also (original owner.) The side stand DOES stay down but the geometry has never really give me any confidence. Seems like one small nudge could knock the scooter off of it. When in public places, I always use the center stand, and in my garage I am super careful when I leave it on the side stand.
That being said, the Super 9 is an outstanding, fun vehicle........
Wil B.
Broadview, IL
'71 Guzzi Ambassador
'91 Nighthawk
'04 Kymco Super 9
'11 Kymco Yager 200gt