I will get a pad of 5ml wet media dura-lar. Got in this far, might as well try one more! The NaOH treatment definitely works but if we can get rid of it, so much the better. Another thing I think that might have something to do with stripping and frilling is pH of the NaOH solution. The last sheets I prepped I tried using a 1.0M NaOH solution rather than 2.5M. After processing a few sheets, I didn't think it was doing a great job and on a hunch I checked the pH which IIRC was around 11.7. NaOH should be higher than that, I think. Possibly the terepthalic acid and ethylene glycol are lowering the pH. After the NaOH sat in its jug over the 1 1/2 weeks since going on vacation, I now note a layer of grey powder or crystals on the bottom of the jug. I'm guessing this is terepthalic acid.
WRT stressing the coatings, yes.
1) Soak in an alkaline solution such as your favorite developer and see how long it lasts. At cut edges the water seems to work in an under the gelatin is adhesion is not good. This test is mine.
2) The scotch tape test: Take an x-acto knife (or similar, but razor sharp) and a ruler and cut across the gelatin. Cut through the gelatin but not the base. Attach a piece of tape, say 2 inches long, across the cut. Carefully pull up the tape to the cut, then rip up the rest of the tape as fast as possible. The amount of emulsion that peels off tells you how well it sticks. No peeling is obviously best. This came from a Kodak patent.
3) Wet stripping test: See US Patent 2014547, Babcock ass. Kodak, 9/17/35 Page 3. There is also a dry stripping test given but PET will not tear in the same way.
If you search some of the patent literature on subbing from the mid-1930s through the mid-1950s you can find a number of different tests. Kodak patents seem to have given the best information.