Trying to customize the Gantt Popovers with Studio... I'm to new Odoo and Xpath, so please excuse my naiveté. 

We're trying to add more information into the Gantt popovers on manufacturing orders. We're using the following code below, however, it's not populating the actual data from these fields (it's just blank, but "S/O" and "Customer" are working as expected).  What field setting do we have wrong?

<xpath expr="//li[position()=last()]" position="after">
<li><strong>S/O: </strong> <field name="x_wo_origin_so"/></li>
<li><strong>Customer: </strong> <field name="x_wo_customer"/></li>
</xpath>

To confirm, these are custom fields and do live on the Work Orders. The fields are populating correctly in the Work Order Form and List views.