Hey Peter,
You may have had your question about concave edges answered already, but if not I think this may be the issue. Under Panel Loops you need to set the Bevel to 0 if you want a flat edge. You can also adjust the Bevel Profile for a more custom look, also in conjunction with the Elevation. I’ve attached a screen grab to be super clear. Hope that is what you were looking for.
Also, I wanted to add that I really appreciated your response to Sean about the detail of character versus it’s coloration and how that ties to nature. I think that was spot on, and I’m glad you answered it thoughtfully.
Thanks, and keep sharing your inspiring work, man!