It looks like I might have been incorrect in some of the information that I gave you. I double checked with one of our developers to make sure I understand what all the dimensions are. The information that I am providing follwoing this is correct:
In the inlet catalog the structure width and structure length are width and length of the catch basin structure itself not the interior structure as I had originally thought. The length and width in the inlet catalog also controls how your catch basins appear in a profile.
If you look in the physical properties of the catch basin itself and you are using a box struture type then you will also see a length and width here. The length and width there are also the length and width of the catch basin. They do not differ from the length and width in the inlet catalog except that they do not control anything in the profile. They are also not connected to the length and width fields found in the inlet catalog. They are essentially there for informational purposes only.
I hope that clears things up.
Mark