Turns out that mine is a 550A, not 550B. No idea whether that makes a difference.
I couldn't resist writing a little article about my transmitter setup.
http://antiqueradio.org/HomeTVTransmitter.htm
Written for more of a lay audience, as most of my articles are. Anyhow, in it you'll find a better scan of the DIP switch chart.
Have fun!
Phil Nelson