I have been trying to model a transition from square to
circle, overal height is 6", the rectangle is 12 x 7.5", the circle
is 3.25 inches and is tangent to the rectangle when viewed from the
top, tangent to the 12" side.

To complicate things there are vertical walls 3" tall around the rectangular opening.

I am modeling only half of the funnel, so the sketches are an open rectangle with fillets lofting to 2 large arcs and 3 short straight lines ( equivalent to 1/2 circle) , equalling the number of line segments in each sketch. All of my models fail because there are features that cannot be unbent. If I model the circular opening with one arc, then the flat pattern can be developed, but there are no bend lines.

If I model the circular opening as located in the center of the rectangle, everything works well..

To complicate things there are vertical walls 3" tall around the rectangular opening.

I am modeling only half of the funnel, so the sketches are an open rectangle with fillets lofting to 2 large arcs and 3 short straight lines ( equivalent to 1/2 circle) , equalling the number of line segments in each sketch. All of my models fail because there are features that cannot be unbent. If I model the circular opening with one arc, then the flat pattern can be developed, but there are no bend lines.

If I model the circular opening as located in the center of the rectangle, everything works well..