The adjustment detail on the back of the Squarepants is a great feature.
The original version has the back belt inserted into the back dart.
This version, Plan B , has the belt starting from the side seam.
The function is the same. Plan B is good for fabrics with stretch because it prevents the side back section from growing as the back belt is tightened.
My colleague Norea came up with this. It is a great idea!