Thanks for all the info. Hammering the nailhead spokes is a much better idea than grinding - I should have thought of that. I've got unused hubs - 24h. I want to build with a modern rim, not Roval rims. I won't have to deal with the plastic washers. I might check with a Spec dealer on the off chance that they can get spokes.

Though looking at that spoke photo at full res, it almost looks ground. I will wait for my hubs to come in the post and experiment with fitting hammered straightpull spokes.