Filling a tube with sand is not bogus. It's a bit 'old school'. Professionals who have the proper equipment don't do it. It was just a thought if you were going to experiment with bending on equipment that might be too powerful for the tube. It might help, it might not. M best friend has been a professional mechanic for over forty years, and it's a technique he's used. He doesn't do tube bending on a regular basis, so he's not invested in the equipment.