Thanks TMW,
I'm looking for actual published peer reviewed research papers that have focused on canopy dead wood. I've searched google scholar, Cambridge Abstracts, J-Stor and others, but haven't had any luck. I've read almost all that Shigo published and understand that CODIT will happen around senescing (sp) branches regardless of whether or not the dead branch is still attached. Shigo, as far as I know, never suggested CODIT would be enhanced by removing dead wood. As for Gilman, if he or any of his students have conducted research on this, I would love to read it. The link to the "gray" literature from Gilman suggests that it is his opinion that dead wood "could" pose a risk to tree health.
Thanks again,
I'll keep looking
Tom