For anyone interested... here's a link to a sailing blog for guy that just did the Kent Narrows in early July 2013:
?Narrow? Kent Narrows, Scary Bridge and Stormy Night at Rock Hall Wall | Celerity Sailing
Not sure what his draft is, but I left him a message and we'll see if he reports back. Searching google seems to indicate that this boat (Morgan 382) has either a 5' or 6' draft. He said his depth sounder read "0" a few times, but he has 6" of play before he actually hits the bottom.
Edit: Here's a quote from his blog regarding the northern channel:
The channel on other side of bridge is shallow....I pass over few spots with depth sounder reading zero (depth sounder has 6 inches to spare before I am on the bottom).....a little bit more shallow and I would be aground! And the channel is narrow...fortunately not too long and then we are released into the deeper Chester River and heading north (~22 nm) to Rock Hall, MD . Relief! I can breathe again.