I'm trying to make this specialty Revit duct commonly referred to as "pants". (See photo). 

Pattern/CID 14, also called "Breeches" look like the most relevant part. However, the only value I have to change is an angle value and not an offset value. 

The angle value causes issues because it causes the duct to turn outwards when all I want to do is offset like the part in the photo. 

Does anyone have a suggestion for this?