Has anyone shot those "Accu-vanes", thats the only name brand I know of. They are hard plastic. 1 to 1 1/2 inches long, clip to an insert glued in the rear of the shaft. They claim is they spin the arrow many times faster than standard vanes or feathers, thus allowing the arrow to reach "plane" more rapidly. I saw another brand with a "twisted" nock slot which begins the spin immediately. Your opinions, please.