Is the extra fullness just down in the bottom left hand corner??
I wonder if the white star could be re-sewn to take in some of the fullness?
I would straighten the sides/bottom a bit more before binding the edges. I think some of that could be eased in w/ a cotton batting and the quilting - W/ cotton batting, when it is washed, it'll wrinkle up and maybe make some of the extra not be so noticeable.