Divide hammers into sections according to the action or top stack. On the hammers of two ends of each section, mark where to drill on jig of choice. Connect the drilling points through the whole section.
Drill, trim hammers to length, cove, taper, and sand arch at tail.
Mark strike point on end hammers of each section, hang them as guides according to new design or original hammer position.
Hang the rest of the hammers aligning with the guides. Then trim the hammer shanks sticking out of back of hammers (not shown in pictures).