[jQuery] adding extension property to jCarousel

I can add extension methods to the jcarousel add in such as:
jQuery.jcarousel.fn.extend({
    position: function() {
        //alert(this.first-1);
    }
});
jQuery.jcarousel.prototype.position = function() {
    //alert(this.first-1);
};
but I want to get access to the "first" property of the jcarousel.
Since I only have one item at a time visible and scroll one at a time
"first - 1" gives me the current position of the carousel.
Otherwise in several places in my code, I have to declare:
var position = carousel.first-1;
or always use carousel.first-1 which is not intuitive.