Please be award that buying the insurance when shipping rarely results in them paying the claim if the worst should happen. You will need documented proof of the quilts value which means getting an appraisal. I have heard horror stories of UPS and USPS not even honoring appraisals and reimbursing only for raw costs of material, long arming services (if you had it longarmed) and batting and then only when you were able to provide receipts for them. They do not reimburse you for the labor hours you have invested in the quilt. Many show quilters buy riders on their homeowners policies but you are then talking about quilts that have appraised at thousands of dollars.
That said, I have shipped a lot of quilts all over the country and have always had great luck with USPS priority mail. It is the most economical and they provide a tracking number.