the overflow elevations of the two structures are the same as are the outlet pipes. They are twin structures.
I did run the pond thorugh one 4' stucture and can see that the stage discharge are all exactly half of the 8'.
I have a pond with two separate 4-foot diameter riser structures with their own outlet pipes. They each have a square weir cut into the top and then the top will be open and act as the overflow weir.
I simply modeled this as an 8-foot diameter structure with all the particulars and modeled it...
