LGA-ATL on DL might be a good MR in T class. You'd get 50% MQM with Worldperks, and according to great circle mapper (http://gc.kls2.com), its 761 miles between the airports. On DL website I was able to book numerous same day RTs for $176 (everyday is available on the fare except Sunday and Friday). With the multitude of flights offered, it'd be less than a 6 hour round trip.