I have done a number of them, prefer leather.
unbacked Alcantara can be good too but not cheap.
I have primarily done the Cinelli Unicanitor saddles that require a dart sewn at the nose.
I also have the leather skived thinner, .6mm works very well. .8 is workable
typical auto upholstery leather is 1.2-1.4mm

there are old threads that can be reviewed with images.