One of the drawbacks to using this type of clamp is that they are unidirectional. Not any more! If you make four of them and put two per side you now have ‘push’ and ‘pull’ clamping action. This is great for card scraping. You won’t believe the clamping ability these things possess! Video.
I made a SketchUp file and made a template that you can print out and make your own low profile spiral clamps. You can purchase it here.