Kayaks on Aluminess rack with integrated rollers, Yakima rack with cradle and rollers, and security strap attached to a clamp that fits on our front bumper tube (see link). Our tube on front bumper is 2 inch inner diameter. This clamp fits well, but I will probably attach an eye bolt to it because it will be easier to feed the strap.
It took me a while to find these clamps, but fortunately they exist! They are used for aluminum stage building (trusses etc.), attaching lights etc., with hundreds or even thousands of pounds of load rating.
Pay attention to outer vs. inner diameter of the tube you want to clamp it to and compare it to the specs of the clamp. There are several manufacturers and they have clamps that will fit different diameter tubes.
I could attach strap directly to bumper but I think it will rub off the powder coating. In addition, with the clamp there is zero movement of strap to the side where the tube bends closer to the vehicle which would loosen the strap. But maybe there will be none of these problems. I just liked the idea of avoiding these potential issues.