Good for you, Brad; it takes some courage to raise this important issue. This is an investigation that is long overdue. The temptation is great, but all of us should do our best to resist replicating or creating hagiography, and instead try to search out and produce the most accurate account of our ancestors and their stories that we can, even if the picture the stories present may not always be a pretty one. The truth (or maybe I should say, truths) may not be stranger than fiction, but it is more human and I think more interesting than blameless lives of virtue and heroic tales.
My mother's family were post-slavery immigrants to the South, but as they ascended to the middle class, they became participants, as did their friends and extended family in the racist landscape around them, primarily through their use of household help. This involvement also has a complicated legacy that lives on to this day.
Have you thought of (or perhaps are already doing so) also approaching African American genealogical organizations and historical societies and online discussion groups to come at the investigation in the opposite direction--that is, to see if some of their members or subscribers have encountered DNA matches with descendants of Jewish slaveholders? It's also question might be posed fruitfully to Henry Louis Gates Jr., of the Finding Your Roots fame, since he hosts descendants of slaves quite often on his program, and certainly has included guests with Jewish ancestry.
I do hope that you'll get many helpful responses to this post and hope you'll keep the JewishGen discussion list apprised of your progress.
Teaneck, New Jersey