In the best lock tests, such as those in "Cycling Plus", the best five pound u-locks do as well as the ten pound chain locks. So, I don't see the point of using a chain lock, unless you park in neighborhoods where there are no available locking posts that fit a u-lock, and you need to lock to telephone poles or something too large for a u-lock.
If you park a clearly valuable bike at the precise same location for hours every day, sooner or later a "pro" is gonna see it, and take it. If you have to leave your bike out of your sight for hours, have a second bike that LOOKS like an old piece of junk (even if it rides like a pro bike), and always park it next to new Cannondales.