https://www.reddit.com/r/typewriters/comments/1ov02h8/backing_material_2/

Experiments with different backing sheets in typewriters.

A Shore A 60 silicone backing sheet wasn't a great improvement. A 0.3mm TPU sheet with 75A to 80A may prove better results?

https://old.reddit.com/r/typewriters/comments/okjtab/typewriter_pad_recs/?sort=old