Notion? I'm not sure this actually qualifies as a notion but it is my new favorite - um, thing (?). They're called side grips and make long-arm quilting even easier. My HQ16 came with typical side tensioning clamps but they didn't tension evenly. This system provides consistent tension along the side edge - no puckering.
Side grips are part of the Leader Grip System. Dawn, at Springwater Designs, sells them. I will not quilt again without them!