Not sure if I have anything on your family or not but will check when I have a chance. Do you have any information on the ancestors around Hesse as I would like to add it to my files so that we can eventually match them up. Do you know where in Hesse they came from? - Hesse is equivalent to a US state.
Have you gone on to the Facebook group, "I'm an Umback....and I'm okay" It was started by some of the family that went to Australia and changed the h in the name to a k. There is information on the site about the original town of Umbach, near Kassel, Hesse.
I am working on an Umbach reunion in Edmonton, Alberta, Canada in August so am a little swamped at the moment but will get back to this project after that.
You can reach me directly at firstname.lastname@example.org