rob755: the max depth is 10" The "usable" depth depends on your gear inside. Since the SKB is not a full open back the speaker/power connectors may interfere with the rear lip thing.
I will get picturers up as soon as I get home from work today.
I think pictures would clear up the back end thing for me too! thanks!
Here are some photos of the back. The cut I put in it is about 3" long. It is in the perfect spot to connect speakons to a GK 700RBII or 1001RBII while it is in the bottom spot.