IMU Orientation

I'm building a quadcopter using arduino and a MPU-9150 IMU. With the way things are going so far, it would be nice if I could mount the IMU upside down. I've read that the IMU should be placed closest to the center of gravity as possible, but I haven't found anything regarding the orientation of the unit. Will anything get messed up if I mount it upside down, or will I just have to take the orientation into account when I'm using the data?

Thanks!

just have to take the orientation into account when I'm using the data

Correct.