Eric:
Good start.
There are some other resources you should be aware of that may make your life a bit easier:
Great online resource -
http://maltesex.com/plating/This is a database of lots of scans of plated penny blacks. When you think you're close, you can go to this site and, by typing in "leftx righty" in the search box (where x and y are the letters on your penny black), you can see examples of that letter combination that you can match. More instructions are on the front page of that site.
Additionally, you might want to invest in a set of the plating CDs that are available on
ebay. They would give you similar scans of the penny blacks to help with your plating.
Lastly, there is a yahoo group - "plating" that you can join where group members help each other out with problematic plating questions. By posting a scan to this group, you'll have access to lots of really good platers. join at:
http://groups.yahoo.com/group/plating/Good luck and have fun!
Chip