Hi Burr, yup a blend like that is a good option if you want to have a more semi-organic feeling corner rather than one that follows an exact circular arc profile like the one I posted.

You could do a surface blend like I think you did, or also if you use Edit/Separate on the original rounded rectangle then you could delete the arcs from the corners and put in some curve blends in those spots to make up the sweep rail.

- Michael