https://www.facebook.com/groups/TypewriterCollectors/posts/10163311006014678/
Some interesting 3-D printing advice for replacement typewriter feet here.
Zach Hubbird recommends using a filament dryer and Shore A 85 (or lower) TPU from Siraya Tech as 95A isn't great. Many feel that 95A isn't as "grippy".
Erik Bruchez also recommends 85A while Marty Morren suggests 70A and is contemplating sourcing 60A in the future.
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://en.wikipedia.org/wiki/Rehbinder_effect
can be leveraged to cut glass and make flint easier to chip off (Indigenous peoples used a variation of this to create arrowheads - source?)
For platens 83-98 Shore A depending on the amount of copies being typed. From personal experience though 83A is super soft and the slugs sink into it a bit too much, the sweet spot is around 87-90 Shore A imo.
via u/Pelicram at https://www.reddit.com/r/typewriters/comments/1cg6e3t/platens/
The platen was quite hard to begin with, around 100 on the Shore A hardness scale, though it would feed two sheets reliably. The platen was cleaned and treated with methyl salicylate, which brought the hardness down to about 92, and has remained at that hardness for several months.
https://typewriterdatabase.com/1948-smith-corona-clipper.21427.typewriter