Go with a 12'--I have a 14' and have only needed the huge size a couple of times, but definitely use the "12' " span as I sometimes will put quilts one going lengthwise for ease of quilting. also, mine has casters but quilt in my basement and have office type carpet on the floor and there is no way I can actually move it--it's a beast! I have friends that have 12' and due to room size, have them at an angle in the room to allow space around one end and front/back. Love my long arm so if you can--go for it!