It is what you describe. However, Rocksim doesn't allow for an elliptical fin choice. But Rocksim does have a "chamfer radius" button. I re-read the definition of that option, and it is the method to round the sharp edges of a fin design. I still don't remember using it before, but apparently I must have.
Thank you- your response made me go back to Rocksim and check the definitions of all the buttons within the fin design mode.
TRA #12430 L3