Colleen called me this afternoon and made a few suggestions. She suggested first that I use my NYB pieces as templates and make exact replicas using scraps. Then I'd see if using a single fabric instead of a pieced one makes a difference. And secondly, to put the concave on the bottom and the convex curve on the top. I had been doing the reverse.
The fabric pulled apart a couple times
and I had to rip and resew. In the end I had this
The yellow fabric is almost a quarter inch longer that the navy. And now the NYB
And now the yellow is too short.
Here are the two pieces placed one on top of the other. Keep in mind that I used the orange/yellow stripe as a template to cut the navy and the yellow fossil fern as a template for the yellow with black dots. So why would they be difference now???