I am speculating the opening might be narrower with the shorter box because the swing arm would be shorter and it is the swing arm that is the limiting factor.
The two bottom pictures are an attempt to show how much opening there is on the right hand Sprinter door. I have no idea how the images got turned upside down when they were uploaded.
On a side note there are three, count 'em three, latches holding the Stowaway in the closed position.
- A pin that drops into holes at the hinge of the swing away mount
- A spring loaded block on the left or free end of the swing arm
- A screw in bolt on near the spring loaded block
So it is highly unlikely that it would come adrift, however I have had to add an item to my check list to tighten the screw in bolt at every stop. It will vibrate loose and so far I have not come up with a good way to prevent that. The answer is probably a good lock washer, but so far I haven't found one that works.
FWIW I am very happy with the Stowaway II Max. It is capacious enough to swallow a huge amount of easily accessible gear. In fact it would be almost too easy to exceed the 200 pound weight limit (125 pound using 1.25" receiver).