I believe they are 1/2" brass #4 wood scRew. I check my screw charT FOR SUre. The mouse pad and weather stripping sound Good . I was going to find a piano repair shop ,they should have felt.
One more question: do the two acorn nuts (or whatever you call them) on top of the mute come off? I want to know before I completely screw mine up, would make it a lot easier to experiment with material for a mute.
The acorn nut does come off. I believe it also unscrews at the base. The acorn nut might be jammed against the stud causing it to unscrew from the base...........On several of mine, the two little screws that go in from the back side had come loose. They hold the nylon slide tight. You have to get behind the paper sticker to tighten them up. A good thing to do if you need to before it is installed.