Right. I have never had any problems at all when originating in the U.S., even if the overwater carrier is going to be a foreign carrier with a lower allowance, and the first hop is only a shorthaul commuter flight on a more generous carrier.

Where I have run into problems occasionally in the past with different carriers is starting a trip in Europe in the reverse situation - a short-haul connecting flight with a stingy European carrier whose check-in agent, even though it may be very clear on the ticket or in the CoC, nonetheless tries to insist on applying the lower allowance of their airline rather than the transatlantic allowance of their alliance partner operating the overwater segment. I have had quite a good battle with Lufthansa over that, actually.

For my travel this week, I have armed myself with the documents you all kindly supplied, and will avoid carrying the normally-allowed additional 20 pounds in each bag, just in case.

I do find it interesting that the luggage allowances you have found described by Air France in their official terms do not consistently agree with the results returned by the luggage allowance calculator provided on their web site. Of course, they would not be the first airline to be IT-challenged...