Keith Dishman maintains the Dishmanweb and has been in direct contact with the French Dishman descendants of Samuel Dishman and his older brother - both of whom were Huguenots.
There is also a thoroughly-researched Dishman Index published by Charles Marsteller and James Dallas Dishman, both descendants of Samuel DuChemin/Dishman. There are copies at the Library of Congress, DAR library in DC, LDS in Salt Lake City, Sutro in San Francisco, and Allen County (don't know if its the library or genealogical society) in Indiana.
I also have a copy if you have any questions that can be addressed by it. Charles is still around, too, but I don't know how digitally active he remains.