Just to confirm that I got this right. If you book an award in C and part of your trip involves flight within the US/Canada/Mexico where only Y and F is offered you would be sitting in F or Y? I always thought that they'd downgrade you to Y on a C award and only sit you in F if you have booked a F award all the way (of course, if you pick a 3-class plane that offers C you'd sit in C).
Do I get this mixed up with the revenue RTW bookings? Maybe it makes a difference whether you book an international award with a long haul C class or a domestic award only?