If you don't care about the looks of all of the wires everywhere, you can put it on the top, right side up. This will allow easier access to the button to program the gyro. However, if you are like me and you want the cleanest looking helicopter possible, then mount it under the heli. this is the way I do all of mine if I can. But ultimately, it's up to you.
Let us know what you think about the Dom, I have not had the pleasure of seeing one in person yet.