Haven't done this, and I'm not an "experienced" long armer but ... I might consider floating the top and the batting. Then I would machine baste across the quilt and to edges - one "row" at a time, working your way down the quilt, and making sure to at least "tack" the outside corners.
The reason I would baste across the quilt it to retain the integrity of the center. If you only basted down the sides you could wind up with the center shifting.