Increase the speed of scrollbar stepper scrolling?

I use a laptop. I have this:

 -GtkScrollbar-has-backward-stepper: 1;
 -GtkScrollbar-has-forward-stepper: 1;
 
set in gtk-3.0/gtk.css, without which scrollbars are unusable.

But, at least in whatever configuration is unchanged by me in fedora
22, the stepper button scrolls text at a rate of one line of text per 5
seconds, which is also unusable.

Is there a way to have usable scrollbars that would generally work for
existing gtk-3 applications, i.e. configure steppers to scroll text at
a speed that would be typical of gui applications in windowing
environments? I notice that scrollbars in firefox scroll at what I
would consider a normal speed when using the stepper buttons.

Kendall