so, i really don't understand i guess; when i trim/square up a quilted quilt i always cut it even...top, batting, backing. then to make binding, bias or straight. i use either 2" or 2 1/2" strips, fold in half lengthwise wrong sides together; press. line up raw edges on the front of the quilt with raw edges of folded binding. stitch 1/4" when i pull the folded edge over to the back for hand stitching the binding is always 'full'; it has the 'sandwich' inside it.
i do always ask a quilt owner if they want me to trim it for them when i finish quilting it, but never thought about someone saying yes, but not wanting it trimmed even.....now i have to think about this; and a question...
if you do not trim it even after quilting how do you trim it?