Back when Epic Malibu was being used by BD, adjusted a hose nozzle to narrowest and strongest setting, and held it a few inches from the fabric, stretched taut over a plastic embroidery loop, for a minute or so. No wetting out, no penetration.
Then attached another swatch in the loop over a pail, and left it in autumn rain for over a month. It was a rainy fall. Checked regularly. Only slight wetting out, no penetration, after a month.
Then Roger tested a swatch for me. Good to ~1500mm HH, then became a sieve.
Shortly after that we got a record heavy rain. The fabric over the pail wetted out, and there was maybe an ounce of water in the pail.
That's when I realized how much we owe Roger and Richard.