I use a machine flange welded to a stainless steel 3" 90° pipe for the school buses. They work quite well. The OEM for the bus DP and our application is a flange that is simply pipe bent back over its self. The weld in flange/machine cut is a bit thicker.
Our trucks OEM DP is stainless steel of some sort. And the cheap flange is welded in place. I have never seen a flange break on our trucks, however the pipe its self will crack. The school bus flanges will break off so I use a section of flex pipe down stream now.