Its somewhere between 30-40 but it looks closer to 40 so I just call it "The 40"
I used coco panel (for lining plant baskets) stuck to the GS when it was most sticky. I did have to tear it up to get complete coverage, and need a tad of silicone at the end, but it REALLY reduced the amount of silicone needed in the viv. I like the idea of that. I have got a construction journal in the P&C forum, though admittedly bad.