This one hasn't fallen apart (yet) and the kiwis don't seem to build boats from anything else! Is that amount of work hardening down to poor workmanship/welding? (no offence intended to anyone!!)
They dont have 3 600kg engines mounted solid and on surface drives, 13mm top grade alloy would just split for over 300mm with in 1 hour of racing. When new we had no problems like it. An amazing thing to go in when rough 50ft long and 8ft wide just no stopping it!!