I used to use them years ago, great for getting out of wind which inteferes with swing tips anfd quiver, I'd make them out broken umbrellas using the hinge in the spokes. Theptoblem with them is that if they are fixed on the line they interfere with casting, if they have to be connected to the line afier each cast you might as well clip a bobboin on the line. Bobbin s can be made in a wide range of wieghts and with a lenght of pole elastic in the "string" can be made to suddenly provide some resistence after set length of free movement, the 2string" cna also heve a wieght on it so there's a sudden resistance.