Shading seams in tiled environment models

Coding
1

i have problems with normal seams on tiling enviroment poeces, which come from non-matching tangents. as the shader calulates those with a combination of vetex normal(which i match) and uv coordinates i can’t find a solution to avoid seems. uv splits wreck the tangents, which can’t be altered in maya.
does anybody know a solution to the problem?

here is a link to the polycount thread, as it shows some pictures, but knowbody knows a solution:
http://www.polycount.com/forum/showthread.php?t=119823

2

In your screen shots, is in the same mesh that you have but rotated?
I can duplicate the look you experience quickly in my Max viewport, but the difference I see is not a seam of the textures but the lighting difference by the surface normal.
This is an expected result to me. I do not see any issues on the top faces.
As per your calculations, can you calculate the average between the two sets and apply them to both to alleviate your problem?