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it looks like the code takes this into account

Source file is here https://github.com/ros-drivers/um7/blob/indigo-devel/src/main.cpp

// IMU outputs [w,x,y,z], convert to [x,y,z,w] & transform to ROS axes
    imu_msg.orientation.x =  r.quat.get_scaled(1);
    imu_msg.orientation.y = -r.quat.get_scaled(2);
    imu_msg.orientation.z = -r.quat.get_scaled(3);
    imu_msg.orientation.w = r.quat.get_scaled(0);

so looks like you put it with the x pointing forwards from the robot, fixing the device so the it looks the right way up from its packaging - the code flips the values round to match right hand rule.