I added this to an old tiny Kala Soprano Travel, tried it with a Boss amp, and it seems to work quite ok, no feedback unless volume is really high even if I stand in front of the amp, it seemed to pick up "some" extra sounds mostly from the cable but that stopped after I used the provided pin to keep the cable from dropping on the floor. The sound is not incredibly loud but quite decent, superior to others similar gizmos I tried in my quest to electrify this tiny travel uke.
One note, because I wasn't expecting it: I put it under my usual strings (Aquila Reds) and the string tension greatly increased, making the strings a bit to tight and not very pleasant sounding, so I think I need to get other strings that are more mellow, not sure if it will work, but this is the only downside / a characteristic rather, I hope I can work around it.