Nylon-stringed instruments need a transducer pickup. Acoustic guitar sound-hole pickups do not work. They are too big anyway. The problems with stick-on pickups, in addition to being possible to knock off the instrument if you move around much, is that they are noisier then internal designs. If you are a sloppy player, recording with one will tell you right away. Aldrine can use them successfully because he has superb technique. I'd opt for an internal pickup and among those that work on the ukulele, LR Baggs are the best in my opinion. They are not cheap, but they are worth it.