I bought one of these K&K Sound Rockabilly Fingerboard 'Clicky' Transducer (Pickup) for Upright Bass at Gollihur Music - Double Bass, Upright Bass, String Bass Specialists but have not been able to get much out of it. I have a small 2 input high Z mixer. My regular bridge wing pickup works great but I get very little output from the f/b pu when slapping. So far I've only tried a couple of pu positions, both on the underside flat part. I'm thinking this does not move as much as the scooped out end nearer the bridge. However fitting a flat piezo to a scooped surface is problematic. Any thoughts?