Using 3.2:1 aspect ratio, best way to make this work?

I am creating a 15 minute project of still images moving to composed music in a program called Watchout . The software uses 3 projectors which overlap to create a very large, high-resolution image. The final resolution for it is 1920x600, which is a 3.20:1 ratio.

I want to duplicate it in Motion 2 for DVD. What is the best way to achieve this aspect ratio? It seems rediculous to use a Widescreen filter on each image, especially considering it only goes to 3.00:1. My best guess is simply to add a layer with black rectangles at the top and bottom. Will this render nicely? Is there a better way to achieve this?

Thanks for any suggestions!