Thanks - yes good advice. The CD is temporary. I'm planning to make a wooden soundhole cover in the future with some 1x8 white pine I have in the garage. The pine is soft and easy to shape with a jigsaw and a small router/trimmer towards a Lutehole-type shape. Maybe an oil rub to add some colour. Regarding the sponge above the nut - I did a test with it on and off, and it clearly kills some wolf notes. There are so many sounds that come from this sweet lovely acoustic bass. The sponge cleans it up a bit. I had to do the same thing with my baritone - the thicker strings bring some overtones.