I went a bit overboard. I thought the default hammering size for a hammer was a 3x3, and adding 3 hammering would give me 6x6 at most. NOPE… adding 3 hammering to
Thor 308 Copper Hammer Size a - Dead Blow Hammers - Amazon.com
C.S. Osborne Split Head Hammer Size 2 Rawhide - Leathersmith Designs Inc.