Find a way to constrain the union base and top base rightly to two reference plane without constraining to much the model.

[mzmaso90]

In the way to create a duct family tee, with transiction  fitting duct, circular   into a T-Junction rectangular, I need to overcome the acknowledge of these reference planes behaviour, more than what I understood online reading the   autodesk manual and become a skilled in  making parameters and T junction Duct. 

As you can see, is not properly created. I tried to constrain, equally, each side of circular form to the referenced plane,  But I still do not understand why shapes are not well constrained. Anyone could help me? <i attached the .rfa family

Best Regards 

[ToanDN · Accepted solution]

Turn on centerpoint for the circle and constrain it.