Guys -

I think the larger air activated containers were hauled five to a car in the NYC USRA gondolas, while the smaller (ie., shorter in height) air activated containers were hauled six to a car in the same, but differently equipped, NYC gons.  The six smaller-container cars were placed in service in about 1937, while the five larger-container cars were placed in service in about 1945 - this is the car in the "builders photo" that was linked here in a previous post.  The side cutouts on the gondolas, and the spacing of the floor positioning angles were different, depending on whether five or six containers were hauled.  I have never seen a photo of a mix of tall and short containers in the same car - what do you think??

A.T. Kott