Foam packed under the bridge just doesn't sound right. If you have a Fender, get a bridge cover, the curvature gives it a nice even distance from all the strings. <a href="http://www.kingbass.com/">David King</a> says the rectangular foam keyboard handrest pad you can get from any office supply is made of the stuff (he warns to give it the squeeze test before paying), and I went and got one, and yeah, it's the stuff, just $8 or so. Try as hard as you can to inspect a vintage Fender with the intact mute. If you take my advice based on my faulty memory, you're in for a lot of trial and error. OK, you were warned. You want to cut it about 3/8" or 1/2" thick (if I remember my '63 P right), about 1/2" wide, and as long as the upper inside surface of the cover. Starting at the G string end edge in the middle, cut the corner off straight ending at the long edge halfway between the D and G strings (the idea is to have about 2/3 as much foam muting the G string as the rest; I can't for the life of me remember which side goes toward the bridge, you'll have to try both ways). Try playing it, listening for the best sound. Adjust thickness and positioning inside the cover as you go. Keep cutting new ones until it's just right, you have lots of chances in one keyboard handrest pad. Use Weldwood contact cement on both surfaces, wait until dry to touch, and then very carefully position the two and smack 'em together. If it's wrong, rip it out and hope it doesn't frag. If it frags, heck, make another.
