Infinite vertical scrolling menu

1

Hi,
I am using POMs tutorial for making an infinite menu
This one is vertical instead of horizontal.
The MC is 1696 pixels in height. registration is top middle
i drag 2 of these MC’s so one is below the other (total height 3392)
Here is my code

 

onClipEvent (load)
{
   ycenter=848;
   speed=1/10;
}
onClipEvent (enterFrame)
{

   var distance=_root._ymouse-ycenter;
   _y+=(distance*speed);
   
 if (_y > 0) _y=-1696;
   if (_y < -1696) _y=0;
}

The clip goes really fast and is making me foam at the mouth if i look at it for too long!
I tried changing ycenter to 300, and it is much smoother but it is very jumpy when moving back to the position determined by the code.
Any help is great