M3 Lip spoiler too long. Anyone have this problem?

Hey Everyone

I just got a M3 Lip spoiler but its a tad too long. I'm just wondering if it was just me, or did anyone that purchased a M3 Lip had the same issue. Its about 3 cm longer and it would look really weird if i didn't modify it. It would hang off the edge of the trunk :?

I plan to cut/trim the outter edge to fit, but i'm afraid it would be all choppy on the edges as its suppose to be round. If I go ahead and trim and sand it, would the sanding make the edges worst or does that depend on the sand paper? I only saw two Mazda3 sedans on this forum with a M3 lip, one was grey, and one was black. The grey seemed to be too short, and the black seem to be perfect.

Anyhow, any help will do.

Thanks!