One thing I should note - from the appearance of the .cfg files, tonnages can be randomised by different amounts which can be specified in the file.
I'm not sure if the variable is for the percentage by which the tonnage varies, or the actual amount though.
Assuming I am correct, it is another SHIV feature with which I am very surprised and pleased.
I've always missed this feature since AOD, and am glad to see it back.