30 minutes will be cutting it close but you will probably be able to manage it. When we did this the MSP flight was the best. I would avoid the ATL flight if I were you. It's very long, and the distance is at the edge of the range capability of the 747, and if there is any profitable freight to put on the plane they will send it and earn the revenue from it and then be too heavy to keep the non-revs on board. We tried for three days and watched as they put cargo on and even pulled passengers (non revs) off the plane. The MSP flight is closer and can be filled up. Also, you can try seattle or portland. You probably won't get lie-flat beds on any of these flights, as we learned on both the 747 and the A330. Finally, I might be wrong on the NRT-ATL flight regarding the cargo — maybe it only applies to ATL-NRT. Good luck!