If you buy veg-tanned leather in the 3-6oz range, the PG settings for leather work just beautifully. If your leather is significantly thinner or thicker you may need to raise the speed, or run the cuts multiple times.
Chrome tanned leathers, or some faux leathers can also be cut just fine, though they have other complications.
Finding settings involves testing - start with PG settings and adjust using something like these until you get it just right.