What fill should I use on leather?

[themainethread]

I am using Design Shop Pro and I know on leather you are supposed to use less needle penetrations but I don't know which one has less.

[gcannon]

I just use the default with the stitch lenght at 40-45 points, and a density of about 3.8; however this depends on whether I'm putting black thread on a black vest (4.0) or white thread on a black vest (3.2 or lower). It all depends on the color of the leather not showing through.