I recently earned DL Silver and am thinking about matching to CO silver elite (and, by extension, Star Alliance Silver). Question is: I have a roundtrip award fare on TAM booked using United miles (a Saver Award) from JFK-GIG around New Years time - if I am Star Alliance Silver through CO, is there any chance I could get upgraded on the TAM mileage flights? If not, I may match anyway because I'm ready to ditch DL, but this would provide some extra incentive to burn the once-in-a-lifetime match.