One of my friends made a quilt that was supposed to have a scalloped border. She was unsure about how to proceed and decided to call the lady who long arms her quilts for her. The lady who did her long arming asked that my friend just add a generous border to the quilt and leave it straight. The long armer volunteered to quilt in the scallops if my friend would trim out the scallops after the quilting was done. The quilting was gorgeous. It echoed the scalloped edges several inches back into the border. My friend cut the scallops out and did the binding. That was one beautiful quilt!
What I learned from this event is to quilt before you start doing any cutting on the scallops. Drawing where you want them to go will give you the visual aid you need to keep your quilting where it should be if you are doing the quilting yourself, which would be my preference.