How to Center Background Slideshow?

Goal: create a CENTERED Full Screen Background Slideshow, with Nav buttons on top.
Using Visual Slideshow1.5

Problem: Slideshow is always left justified. However, when testing a static image, the image is centered as expected.

1. What code controls this behavior, where should I look for it?
2. Where is the best location to have the HTML Placeholder code: Mouse Off Layer, Page background or Pasteboard?

Thanks!