Lo-Fi Games

Hello all.
I made a custom set of textures for personal use, and they almost completely seamless, but only if I use them with vanilla heads.

But when I trying to use them with custom modded head from this mod, for example - seams suddenly appear.
I even changed UV map of the head from this mod in Blender, (it was snapped to symmetry), so now it looks like vanilla head UV map.
Does anyone know what could be wrong with custom meshes? I spent a couple of hours trying to find something - and with no luck.

Well, after some research, I discovered what might cause this bug.
If you try to change the default mesh, then you will get a neck seam.
Looks like you can't change the geometry of the base head (or maybe body too) without getting ugly seams.

But you can edit shape keys without any problem.

So I used this to transfer shape keys from a modded head to the base one (by using a third-party script).
And then I set xml-file with chargen sliders to use this shape key by default.