Why do you want to turn the whole train? How about just the engine as it will save much space.
Here is the track arrangement:
The curves are all O72 RealTrax - each leg has one O72 half curve. The straights are all 10" except for one 3.5". Switches are all O72. Straights come in 10" and 30" lengths so just add however many you need to fit the length of your train.
-Greg