Tested with fresh install, Odoo v7 github install May 2015.

When I create an order with products whose weight is entered, the 'Delivery slip' report always has an empty weight.

The rml report file is : 'addons/stock/report/picking.rml' ( Object is stock.picking.out )

In this report [[ 'weight' in picking._columns.keys() and picking.weight or '']] always return an empty string !

Anyone has information about this issue ? ...  Such as if it had worked, and with which version of the 7 ?