I don't know if I explained the issue quite well. Gavlig the problem is in the edges that are shared with each poly with two different smooth groups / soft edges. They have 2 different normal in the same edge, so I will have always the same error or at least I don't know how to fix it.
If I don't split in 2 smooth groups, then in top view, where polys have more than 90º we will have lighting issues because they will have its average normal of both polys with a normal pointing nearly parallel to faces, You can see it in picture attached there, blue lines are the average normals. Thats why I said to add some extra trys in border of this edges to avoid this lighting issues. I thought the same as you at the beggining, fixing it later on Photoshop, so I baked another NM with only 1 smooth group and copy these wings without seam error, but it didn't work due the tangets are mising information in the angle between them. As I said, I don't know if it is possible to fix it, at least I don't know how atm. Here you have more detailed infor and well explained about smoothing groups issues:
http://www.svartberg.com/tutorials/arti ... lmaps.html
Probably you already know it and you know how to fix it, as I said its my lack of experience solving this kind of issues why I'm asking here for help and advice.
There are other bake errors I can fix it manually in Photoshop with healing / clone/ patch tools and later renormalizing with xNormal filter to solve lighting issues, but this is not the case.
I uploaded an .obj and NM texture so you can check it in your 3D software. NM was with 3DS max preset (X+,Y-, Z+), so if you work with Maya invert Y channel.
https://www.dropbox.com/sh/wqtca0o3thfa ... KVkla?dl=0
Thanks a lot for your feedback,
Sergio