I have just picked up your Genforum(genealogy.com) message n° 685 of 14 Oct 2006. Sorry for the time-span - I may not be the quickest of persons to respond!
Over the years, I have compiled a report of some 720 pages on the family (and family "marry-ins") which I have written with my cousin in the UK (I live in France for the last 35 years - just nearby to where indeed Copsi de Tunstall was born and set forth from nearby Dives-sur-Mer with William the Conqueror!).
I would be delighted to share my findings with you if you would like to mail me at:
To transmit my report to you, you will need to instal the Family Search Personal Ancestry File (suffix .PAF) software from the Mormons - it can be downloaded as a "freebee" and is very easy to use (suits me!) - version 188.8.131.52 from http://www.familysearch.orghttp://www.familysearch.org
I am a direct descendant from Copsi, althiough not necessarily by the eldest child.