Solution : https://service.sap.com/sap/support/notes/874922 (SAP Service marketplace login required)
Key words : 
weight      bapisditm-untof_wght      bapisditmx-untof_wght volume      bapisditm-volume      bapisditmx-volume volume unit      bapisditm-volunit      bapisditmx-volunit numerator, gross weight      bapisditm-gross_wght      bapisditmx-gross_wght net weight      bapisditm-net_weight      bapisditmx-net_weight unit, lme      bapisditm-salqtynum      bapisditmx-salqtynumfor, weight determination occurs, entered weight, weight specifications, measured weight, sales quantity conversion, standard system behavior, standard behavior
Related Notes : 
       
| 797815 | The CRM_DATAEXCHG_BADI data exchange BAdI | 
| 170183 |