No- never did. It would take a LOT of grease to fill up the space. Might even affect front wheel balance. The rear seal (not included on all Panteras) is not that great at sealing even the little grease actually needed. There is no front seal so you'd have to adapt one somehow or the rig would throw grease everywhere when things got warm in operation.
If the stock front bearing halves are properly hand- greased every few years, they last a LONG time. I'm running OEM 1972 bearings in lightweight aluminum hubs. I learned to hand-grease wheel bearings when I was 16- in a different century!