Something further regarding my dish-warped Achromat. I just read the blurb sheet that came in the cardboard sleeve and it says this:
Occasionally uneven cooling results in minor warping. Like tyres, regrettably the material does not respond to being re-formed.
At least they do say: If your mat is deemed to be warped, let us know, we are happy to replace it.
Guess I'll be sending this one back. Sucks after waiting weeks to receive it.