Customizing sticky header

Hi everybody.
I would like to know how I can customize the sticky header behavior. Reading the javascript, it looks like we can set the direction that add the sticky-visible class to the header nad I think we should also be able to set how much the user has to scroll the page to get the sticky header visible, but I can’t figure it how to do it…
There’s someone who can put mi in the right direction?
Thank you so much!