In a number of Air Route Traffic Control Centers (ARTCCs) around the United States, time-based metering of arrival aircraft is being used to control air traffic demand on busy airports. In attempting to introduce time-based metering for airports in the Northeast corridor (such as Philadelphia International Airport - PHL), several technical challenges were identified. Single-center Traffic Management Advisor (TMA), the most advanced decision support tool (DST) used for this purpose, is limited to managing traffic within one center, and to within about a 250 nautical mile (nm) radius. To overcome these restrictions, NASA engineers designed a distributed scheduling system, which uses a loosely coupled network of schedulers that can be extended across ARTCC boundaries and out beyond 400nm. The resulting design was incorporated into the Multi-center Traffic Management Advisor (McTMA), a traffic management DST whose implementation has undergone research and testing on PHL arrivals. This testing has yielded several key insights into the distributed scheduler, resulting in significant changes to the algorithm and underlying software. Three of these are discussed in this paper. First, the method used to account for and distribute unused capacity has been changed. Second, the resolution of the mechanism used to distribute restrictions has been increased. Lastly, an inconsistency in behavior between how close-in departures were being scheduled as compared to airborne aircraft was corrected.