(a) haven't seen Leon in years .. he ended up in Ansett mainline
(b) don't think DU has been used in civil aircraft .. although a post accident problem from time to time with military
(c) DC3 middle age spread is much the same problem as we all have .. although a good major can go a long way to fixing it up .. best I can recall for a Gooney was around a 400 lb gain by cleaning up the bilges