Sue - The door box "encroaches" into the cargo area by exactly the distance between the Tone/JAMAS cargo box and the rear door. I'm not sure of the exact measurement, but a good rule of thumb would be to say that it sticks in just about to your rear tie downs. Take a look at the pics below, the area between the cargo box and the door (where the rear walls "merge" towards the tailgate) is the area that's consumed by my door box.

JAMAS Box:


Tone Box:




Personally I don't see the advantage of a more shallow variant; since the rear walls curve inward to the tailgate, you probably don't even use that extra inch or two now.