I've been having quite a few issues with trying to place a rectangular takeoff on the bottom of a duct. The main duct is 1500mm X 900mm and the takeoff branch I want is 1600x450 (see top image).
As you can see the duct needs to be offset all the way to the edge of the main duct. This I already know I can't do in ABD. My problem is that I have to jump through hoops just to get this takeoff to be 1500x900. I have been able to get through most of it except that it places the takeoff far away from the main duct (see front image).
It's like it is spacing it as if it were coming off the side of the duct (which is wider than it is deeper). Here are my size settings for the branch.
John K.