Thank you for the example Kraid,
My general understanding of uv mapping and lightmaps are now far better. Unfortunately I didn’t find the way to manually modify the UVW map.
So I exported them to 3ds max and I did the uvw map in it. It look like this resolve the problem even if it is not the best workflow. I mean “dancing” between two different software to do the same process may have worked in this case but doing this in a bigger project or a more complex one will probably slow down the process.