While you won't get the same functionality of fulltime dual monitors, the "Turn on detailed trimming" option should provide some of what you need to see outgoing and incoming shot at the same time. It invokes when you're trimming.
If you have it turned on in preferences, you can disable it pressing the option key. If it's disabled, the option key will switch betwen the end point of the outgoing clip and the start point of in the incoming shot.
Command comma is the keyboard shortcut to turn it on.
The only issue I've found with this is that while it works fine when you use your mouse to trim back and forth, the source/record goes away if you want to trim frame by frame with the arrow keys. This makes it kind of worthless for what I use it for.