I'm not so sure about "Pan Am" just yet. It's situation against "Sunday Night Football" pretty much means ABC would have to abandoned the time slot and find something else to start over with after football season. It's ratings so far aren't as bad as "The Playboy Club":
I have DVRed Pan Am, but not watched yet... I have a lot to watch on Sundays!
My gut says Pan Am has a different audience than Sunday Night Football... so I don't think the typical SNF viewer would watch it if it were on another night... I'm the oddball who is interested in both... I remember watching Ally McBeal instead of Monday Night Football back in the day...
Anyway... I think you're right... ABC probably concedes the night to Sunday Night Football anyway... it's different than NBC putting Playboy up against MNF because while Playboy and Pan Am are period pieces, I'm not sure they were trying to get the same audience.
My gut tells me that Pan Am is hoping for more female viewers, where Playboy was clearly aiming more for the men.