I don’t have specific leather experience, but I have run enough odd surfaces through the press to know that you need to be quite careful with firm or textured surfaces that push back against the type — you end up with mashed metal, or imprinted wood, depending on what you were printing with. I now have some wood type with underpants elastic bitten hard into them! (Long story 🙂 )I think polymer plate would be ok to work with, but the plate should isn’t very deep, so you may end up with the edge of the plate printing as well.Have you been to a leather shop to get an opinion from them about the process?