OK, thank you, these are all helpful comments.
I am trying to determine what if anything can be done to correct the central stars I have now. I am sending photos, not sure if this will convey the issue.
Basically there is bagging and bunching in those central stars, which was NOT there until I set in the final pieces around the perimeters. It's like finishing the perimeter caused the central star to buckle. So is there any recourse now? I have blocked these to get them to lie somewhat flat...
Here are both blocks followed by the centers.