Hi Watson!
I don't know if you're quilting on a longarm or a domestic. I did a quilt with feathers in the border, but I put the binding on first. This was on a domestic Juki. I found it easier to "center" my design.
For the corners, take some time and do some sketching on paper. From your work that I've seen, you're a creative lady and I'm sure you'll come up with something for your corners.
Looking forward to seeing photo.