To fill or not to fill..?

[Romeo]

I have removed old leather from a pair of ash oars. Having repainted the oars I am now ina position to put new leather on. There are holes left where the copper tacks which held the old leather in place have been removed. The area has been well soaked in wood preservative. Views please on whether I should fill the holes from the tacks (and if so what with?) or whether I should just leave them to breathe away under the new leather. The oars must be at least 50 years old, but are in pretty good nick.

 

[Peterduck]

Moisture travels through wood most easily along the grain. For this reason boatbuilders do everything possible to cover end-grain, tp prevent ingress of wood-rotting moisture. Fill the holes with small sticks of softwood, and glue them in place. Finish off smooth with the normal surface of the oars, and varnish to further prevent ingress of moisture.
Peter.