if you want to make it larger than either more tumblers or a border would make that happen- only you can decide if it needs it or not-it's a personal choice. you could if you wanted to add a border by appliqueing the top onto border fabric which would 'square up' the top without having to cut your edge tumblers. you said you need to add either a border or binding ??? generally binding is added around the edge of a quilted quilt to finish the edges of the quilted quilt sandwich...so, even if you add a border- you will still need to bind your quilt after quilting it.