chainplates: round holes vs square holes

[benjiwoodboat]

talked to three non-sailor machinists this week about my cracked SS chainplates. All of them said the same thing: you'd be better off with round holes. both chainplates had cracks at the first bolt. what are the thoughts on this? carriage bolts are nice on the lines and humans, but does it make sense to drill round holes and use hex head bolts? are there solutions im not aware of for this?

http://lh4.ggpht.com/BenEriksen/SAt6...jpg?imgmax=640