Two good posts above, the H48's really do seem to wear easily. I made some in a thicker stainless steel, they take some shaping and remaining dead flat, but seem worth the extra effort. One pair of shoes I purchased S/H had the feet of the shoes bare and with lots of ally seemingly filed off the feet. In the end, I worked out how thick the feet should be (with H48's on ) then tapped threads and screwed 1/8" thick caps on with csk screws. It saved the shoes and is working fine, much firmer surface.
I have had to re-align a few pivot pins, 2 were even loose, and the 2mm stiffening plate , again csk screwed on, ( 1" centres ) helps keep them in line and really does seem to help reducing sponge, needs doing before turning the linings to drum size.
In looking into the issue of pivots moving 1mm, I drew the assy up , actual size. I could see that moving the pivots 5mm (ish ) towards the hub centre would make a difference but only in self servo effect. Always a danger of grab though. What did come to light, in basic design, the centre of the linings should preferably be at 90 deg from a line between the shoe pivot and the centre of the cam. To meet that, it seems the linings would need to be nearer the cam by around 18mm. I might draw it up at a larger scale to check that, but it's very visible.
A local friend is an ally welder, I'll ask him to weld the top end "dips" up and have some linings bonded further up. A job for the spring, the result should be interesting !