It should work fine as long as you use a very low loft batting. I can't imagine trying to fit a cotton batting in that size harp. I have a 5.5" harp and barely fit a twin under it. Maybe the Quilter's Dream Request would work, but that would be the only possibility for cotton. Hobb's Washable Wool would definitely fit, just make sure you have a large flat surface to support the weight of the quilt while you're quilting it.