Uneven cover curl after lamination

[JoshB]

I'm having trouble with sheet warping for digitally printed, nylon-laminated covers. We use docucolors to image and are pretty happy with the quality, but when coverage is particularly un-even, the sheet shrinks in high-coverage areas and causes waviness. Laminating then kind of "seals" in the problem.

Does anyone have advice on how to mitigate this? We lie about the paper weight to lower the running temperature a bit (this helps quite a bit, and hasn't caused any adhesion problems). Beyond that I'm not sure what to do. Can anyone recommend a 200~250GSM uncoated cover paper that is stable with a high-temperature toner-process? Are there any other tricks I'm missing?

Thanks.