congress' approval vs. congress's approval: a thread to hash out the possessive 's s'

Boise's ball (a ball owned by the city of Boise)

While I am well aware of the approved standard I was taught as a lad, this is definitely a standard I think ought to be rescinded. Every way of handling a possessive "s" following a terminal "s" will be ugly, but at least "Charles's" has the twin virtues of being easier to notice and easier to remember, because it isn't a deviation from the general rule.