Gentlemen,
This information helps me a great deal, and I appreciate the wisdom you all bring.
For Woodman:
This is a profile shot of the coaming on my wife's Ravenswood.
It's made of oak and was flat. I then set the coaming onto the kayak frame and wrapped a ratchet strap around it and cranked up the tension to get the flex I was looking for. I suppose it sat there a week or so. It was removed to cover the frame, and I think the tension of the fabric may help it keep that shape.