Chainplate materials

[Brion Toss]

Hello,
And first, that's an elegant little test; why does it work? Is it the length of the unaffected sections?
As for the materials, nickel-aluminum bronze is good, with the only qualifier being that bolts made from it might be slightly stress-corrosion-vulnerable ( Warren ). Actually, a number of bronzes would be just about as good, as would grade 5 titanium, though if you bend the latter, some skill, care, and heat is required. At 3/8" thick, the chainplates are reassuring massive for this boat.
Fair leads,
Brion Toss