always and anyway it is essential to have the sketch of the piece to understand what you are asking us. If I have to fresare frontally a piece, I will prefer to place it in the car in the most convenient way with the tools at my disposal, as long as it remains stable, without vibration and that I do not get to the nose. If I have to do other work, I will place it preferably in a position that allows me to do all the work without spying on the piece.
the position of the piece apart from the safety is not important. it becomes important instead the position if you also have to head. for the flatness of the faces is important to support the piece on rectified and well cleaned exhibitions before tightening it in bite. for vibrations instead you have to calculate well the cutting parameters especially in the grinding work.
