I understand that this probably sounds nuts but it's just an idea that i wanted to float out for comment. I'd love for some guys who know way more about upright than i to tell me whether this a horrible idea or may actually work. I'm having major feedback issues from my cheapo chinese Palatino upright. I've tried EVERYTHING from magnetic pups to EQ to stage position to putting a towel in the body and i'm always left with horrible feedback. I had the idea to fill the body about half full with a type of canned, expanding foam insulation called "great stuff". I understand that this is going to lessen the natural acoustic tone of the instrument and devalue it greatly (from the enormous $500 it's worth now) but is there any reason why this isn't worth a try? has anyone tried this before? Last note, i spoke with my luthier and he told me if it went horribly wrong he'd remove it for me for $100. so all in all it won't be impossible to reverse.