Mine is welded on, the welder complained about the quality of the pipe that I delivered, so he welded it both from the out side and the inside, just to be sure. For the position it is very simple:
horizontally place it so it is right where the exit from the turbo is (yes, you need to trial prefit the turbo for that).
vertically place it as high as possible but so that you still get gravitational flow of the oil from the turbo.
Also place the pipe at an angle pointing upwards a bit.