S'more about the humidifier:
1. You can drill a hole in the side of this humidifier for more exposure to the sponge if your case cover fits too tightly.
2. if you are worried about tension on the strings, just loosen the string a bit. It's no big deal to retune prior to playing.
3. Yes, you can drop the humidifier into the body of 'uke if you want.