Don't see why you couldn't use a very small spinner on a fly rod , except the fly line would twist some , might wreak some kind of havoc with your tippet . Best way to do it would be to tie up a fly that had a small spinner blade (sz.0) hanging off the bottom of it , so it just fluttered rather than spun . I've seen some jigs tied up that way . If you going to go to the dark side though you might as well go all the way and use a spinning rod