Tiled landscapes, how to avoid seams between LODs?

Here is a pick, you can barely see the seams but they are really visible in game. they only happen on the LODS material at the streaming distance and not on the landscape material.

the landscape material is using a pretty simple 4 layer weight blend BP

The layer infos are somehow hooked up under the hood for each tile directly at the import stage and work as intended and pretty conveniently too.
My issues start when I try to replicate this same exact material for the LOD tiles generated in the editor. Where do I plug those layer info textures? how do I supply those layer textures for each instance of the material for each LOD? If I use a an height blend instead I get those nasty visible seams of the first pic.

Also… is there any way to make those LOD meshes stream in not just for the x and y axis but also for the Z one?
I have seen a number or people asking to have some Z based LODDistance factor as you move away from the landscape vertically but It seems something really deep in the engine and it will never be changed. I would be happy just to make the landscape sublevel unload at a given Z and let the LOD stream in. How would I do that with a blueprint?? Thanks