Thanks again for all your help. Today, somewhat miraculously, a lot of dates suddenly showed up with an Excursionist Perk leg availability (i.e., 0 miles). I was even able to get a halfway business class on a mixed class itinerary. It still baffles me how the miles required gets computed because there were many flights labeled as economy saver (class XN) that costed 12,500 miles. I thought those were the lowest possible, surely opened up by a first leg in Business (I). However, in light of the successful result, as a former manager of mine used to say, let's not allow rationality to get in the way of solving a problem
