Dave, I simply pried my old leather loose after slipping a thin bladed screw driver between the plastic platen and the leather. Then it took just some scratching and scraping to remove the left over glue to get a smooth flat gluing surface.
I have good success using 3M Super 77 spray adhesive. I tape off all around the edge of the platen so the adhesive only goes where I want it. The same with the leather. I spray it, then let it dry. Work carefully because it wants to stick exactly where you place it. I do apply clamping pressure to the leather just to assure it’s adhered flat with no loose spots under the leather.
I’ve replaced the leather several times this way and it hasn’t failed or let loose after a couple years use, so far.
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