slider - increasing thumb height

Hi,

I'm using css to increase the thumb height of a vertical slider.
Looking at the code, the slider class should be aware of dynamic height because it calculates this.halfThumb in the onRender stage.
css:

Code:

---

.x-slider-vert .x-slider-thumb {
        height: 100px;
        border: black solid 1px;
        background: transparent url(../../resources/images/default/slider/slider-thumb.png) repeat scroll 0pt 0pt !important;
}

---

The result is that that I can drag the thumb passing the edge and only the center of the slider stops at the end.

Is there some other way I can style/extend the slider to support different thumb size?
Can I dynamically change the thumb size and make the slider be aware of it?

Thanks