Hm.. that's a good question.. I would assume that as long as the spinner is mounted sturdily, the angle wouldn't really interrupt with the centrifugal force since the encoder disc is equally weighted at all points.. like if you take a spinning top and hold it at an angle (same principle -- it keeps spinning).. after a really long time, the shaft might develop a groove from the weight of gravity (maybe), but proper lubrication would probably prevent that, too.