Chris Ghent gave me a bit of help with a trial piano felt to make bushes to go into keys, so that the lever arms are snug. But... as a (learning) bookbinder, I have ready access to fine, good, the right thickness leather from my Maestro that is snug, offers a cushion on the top part of the hole, or if you turn the 'bush', the tiny sausage sideways, to the top and bottom of the hole. Likewise, I can punch out the tiny pads that fit over the pads on the ends of keys. I've done a couple, and my Lachenal has not complained. I don't think it will rot or fall apart quickly.
Have I committed a venal sin?
Thanks
Larry