HI all, This is probably not a big secret here, but I've not stumbled across any discussions about it. I've been using an acoustic fretless in my jazz project. Most of the time it produces a really cool sound, approaching a DB, but I constantly fight with a booming feedback in a couple of tonal ranges and the tonal range can be different on any given day or location, so it' been a bit frustrating. Have not been able to play it with the band without fear that the booming feedback will occur when I try to sustain a note. Sometimes I can EQ it out, but not always. I picked up an acoustic sound hole cover this weekend and man what a difference. I can still get feedback but I have to really try. I was able to increase my volume, choose affects and adjust my EQ to what I want (not just what worked) and play with out fear at rehearsal yesterday. There was no obvious detrimental affect on the sound - would recommend this $11 solution to anyone who fights with this issue.