Thanks to all for the tips. I will follow suit.
I was building a Cozy IV back in the early 2Ks so I have a nice flat table with a very nice glass table on top of it (a table we were throwing away at that time). It makes for a nice surface which can be easily cleaned.
Now, I remember doing flat layups were I would use dabs of 5-min epoxy to hold down the foam and for the life of me I can't remember how I would un-stick the panel afterwards. I tried a few scraps yesterday which resulted in destruction of the foam. I don't know if it is because the epoxy is different (doubtful) or because I am doing something different or because I am dreaming that I actually did that :)
In any case, the number of warped panels is small and they come from the Cozy days (old). Since the Q1 has a couple of layups for funny 3D bend pieces of foam (in which case it would be of some advantage to start with a flat piece of foam) then I am going to get a couple new panels to see how they look and save the older panels for smaller truly flat and more manageable parts.
Thanks again for the feedback,