multiple Heightmap blending

Hey all,
I am working on an Auto Landscape Material and using the Layered Materials approach. As of now, I am blending between 4 different materials:

  1. Concrete
  2. Dirt Pad
  3. Slopes
  4. Mud

Everything is working fine, but my problem comes from adding heightmaps to the blending mask to get good looking height blending like dirt filing in the cracks in the concrete, for example. I would like all the heightmaps to blend together, so I have been “adding” them to each other at each MatLayerBlend node, like so:

Concrete+DirtPad, (Concrete+DirtPad)+Slopes, ((Concrete+DirtPad)+Slopes)+Mud…

But I am not sure this is the best way to achieve this. Then I wonder if I should just height-blend between the previous layer and the new one, with just the new layer’s heightmap and not the result of all the previous ones + the new layer’s heightmap.

Does anyone have suggestions?