Hygrolon pictures?
 

I don't know if this is the right place to post this. I bought various 1/8" (3mm) 320-400 gsm polyester spacer mesh samples, let them stand in about an inch of water overnight, and found they could easily wick 7"-14" (the widths of the samples). The key is to find the right spacing to avoid suffocating the roots, and the right density so that the roots could easily grow through them. One thing I noticed is that all the spacer meshes have a backing that's more dense, and I'm not sure if that would prevent roots from growing through it. I would prefer to put Monto clay or LECA in the center of the mounts to give a bit more space for roots to grow into.

I've seen photos of Hygrolon and Epiweb mounted on styrofoam, but I wonder if Hygrolon has a backing that's the same pattern as what's on the front, with 5-6 holes per inch lengthwise. Can anyone with Hygrolon please post a picture of the back side, and a cross section, so I could see how many threads are running through the middle as well?

That backing is not universal. Neither Hygrolon nor the “AquaMat” version I sold had that.

I wouldn’t worry about it too much, though. Roots don’t actually move through spaces. As cells are added they grow around the fibers of the mesh, not push through it. “How Roots Grow”