As you know, the two frequent flyer programs operate separately at the present time, and their rules differ in various respects. Unlike AA, US charges the same in mileage for one-way and roundtrip award travel. Eventually, the two programs will be merged, but I would be surprised if US made significant changes to its program before the merger takes place. You may need to wait a) until seats become available using AA miles and b) until you can book RT travel using US miles. In any case, it will be difficult to find four or more Business Low award seats on the same flights.