Setup for permanently tilted rotors

We are going to use PX4 on a quadrotor which has its propeller plane at an angle to the frame (that is, its rotors are permanently tilted), the angle is about 20 degrees. That means, that when it’s hovering, the frame is at an angle to the ground.

Do we have to install the flight controller at an angle to the frame, so that it is parallel to the ground when hovering?

Does it make any difference if the flight controller plane is parallel to the external magnetometer / gps or not?

Calibrate it in Sensors>Level Horizon in QGC. Set it at the angle you want to recognize as level then click Calibrate.

Good luck.