well it is just bolted on..but you have to line up the spots that it bolts to...and if you look at the trunks...taillights, and all...they are totally different than the 03-05...meaning that it wouldn't fit flush...i mean in reality everything on the car is just "bolted" on but that doesn't mean that there aren't other issues that are involved in fitment...the shape of the trunk where it bolts to...and where and how much it hangs over also plays a large role
06 with trunk that already has lip built into it (not curved like 03-05) and led brake light
here is a close up of the 06 spoiler...see how it mounts on the flat spots...we don't have those...and there in lies your problem...mounting a flat piece...on a curved surface...and having it turn out to look good..the new built in lip makes it work as well as the redesigned taillights...don't think it would flow well on the 03-05
03-05 trunk with rounded lip (this one has lip spoiler on it)
so the places you would bolt it to are going to be different thus leaving problems there...and the new spoiler is desinged to flow with the new boxier rear end of the accord and i don't know how well it would flow on the 03-05's curvier
Well, the top of the trunk isn't going to be much different as the quarter panels are the same. its the edge where it rolls down the back that is quite different. I would say that it would be possible to fit the spoiler, but it would need to be slid back slightly and possibly some sort of spacer created if it doesn't sit perfectly flush. Harldy "only" bolt-on, but I would say possible with some patience. You could cover both the trunk and bottom of wing in plastic or foil and put a quite generous amount of silcone blob down where the legs sit and set the wing in place. After it dries, just trim it around the bottom of the wing and that can be used as a spacer. Just a thought.