I have used a heat gun to soften epoxy without damaging the underlying plywood.  That's what I would try.  Used the same idea to get the twist our of a hatch.

Ed

   I have been told that a heat gun will soften epoxy and you can get things to move, I personally have never tried but I have heard that from several builders.

Bruce

A series of kerfs cut through the stiffener only will allow you to bend the hatch cover into whatever curve you need to match the deck curve fore to aft.  Once you determine the shape, clamp the hatch cover down with an appropriate spacer and fill the kerfs with epoxy thickened with wood flour.

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   Same hatch cover as previously posted, but showing off my custom wood bungee hatch cover hold down hooks!

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On my WD12 the hatch needed flattening, not curving so I clamped it to a flat workbench and then filled the kerf (only needed one in my case) with woodflour. Also added a stiffener bar to maintain the shape over time. It's been working for 6 years now with no adjustments needed. For curving the hatch, the stiffener should be shaped to match the required curve.

Here the stiffener bar has had its corners rounded and the wooden bungee hooks have been taped on while the epoxy cures. Still using the same piece of bungee cord after 6 years, too. The stiffener is also a good place to attach a piece of line to keep the hatch from flying or drifting away in case it gets loose.

Good luck, and let us know how it works out.

Laszlo