i was using west at the time, five to one ratio. Try glassing a unsupported thin piece of wood. I know moisture plays a role but I think that shrinkage is also a factor and the best way to combat it to glass both sides before one side distorts. It is important to put the kayak back on the form after the lamination on the inside is completed. I hot glue the deck or hull back on until the resin is fully cured on both sides. i would create a external support for the top of the deck that followed the curvature of the fair side, and temporally super glue it down to the warped side, then glass the underside and let it cure and

No, I'm not sure how you do that. I use Uncle Nick's 2x4 internal beam tooling method.
Seems like I would have to create an external set of forms with allowance for the wood and glass, orient them properly on a strong back.

What you describe was exactly what happened to my deck. However, I know the humidity went from ~40% as I glassed the outside to 100% before I started to glass the inside. When I dried out the inside, as I said before, the curvature was reversed until it straightened out.

My guess is that the wood on the uncoated side picked up moisture, expanded and caused your and my warpage.
Note that I glassed the entire outside surface and it was fine until several days later when huge rains and humidity showed up.

I have glassed or even just coated with epoxy for quite a few years without your symptoms.

Care to tell us what resin you used? I use West.