Visible Seams in Lightmaps

Hi,

Maybe someone can help me with my issue,

I'm making a cylindrical object

Here it is in 3dsmax : http://img4.hostingpics.net/pics/2068353dsmaxMesh.jpg

here are my UV2: http://img4.hostingpics.net/pics/764734UV2.jpg

The problem is the result with unity when my lightmaps are baked :

Here are my scene lightmap parameters : http://img4.hostingpics.net/pics/562774params.jpg

and the lightmap itself : http://img4.hostingpics.net/pics/732529lightmap.jpg

I've tried a lot of things, increasing the padding, the resolution and changing General Gi to HighResolution, and also change the Object scale in lightmap to 15, nothing worked The only thing that make this seam disappear (but still a bit visible) is to enable the final gather.

Is someone have an answer why this happened and maybe how to avoid it on cylindrical objects ?

Thank you for your time