I have a snap on tool box, KRA4107 bottom, and KRA2208 top box, loaded with tools, any idea how much it would weigh fully loaded or what the total possible weight to design spec it could be?

I'm trying to design a custom trailer for it but need to know my weight ratings.

from snap-on
bottom
http://buy1.snapon.com/catalog/item.asp?P65=&tool=storage&item_ID=72612&group_ID=17774&store=snapon-store&dir=catalog
top
http://buy1.snapon.com/catalog/item.asp?store=snapon-store&item_ID=82532&group_ID=21745

They dont list a max weight for the top, but Id bet a max weight on the bottom includes the top box