Scrollpane challenge!

I have a movie clip of some thumbnail images in a scrollpane, and have customized the appearance of the pane by editing the ScrollBar Assets. Works great.

Now I want to change the position of the scrollbar arrows, so that they are right on top of each other at the bottom of my vertical scroll track, instead of at opposite ends of the track.

I see that it should be possible to transform the UI ScrollBar on a textbox, and I have tried this (thinking maybe I could do the same on a scrollpane), but the transform I apply does not show up when I test the movie-- instead it just moves the whole scrollbar, without changing its size. I have tried changing its size in its properties and parameters too.