Can't answer that, but, I know that the 303s on a Supermarine Spitfire were set to 300 yards.
Wouldn't "optimum convergence" be a bit of a moving target, pardon the pun? I suspect it would differ a bit between a gun primarily intended for pursuit of ruffed grouse in eastern MN/western WI, versus a gun primarily used for pass shooting sea ducks of the coast.

Best,
Ted