Instead of a quadrangular surface, you can use a B‑spline surface. The shape of this can be adjusted retrospectively, using the integrated help nodes. Depending on the necessary surface complexity, you can create a B‑spline surface with 3 × 3 or 4 × 4 help nodes.
When creating a quadrangular surface, RFEM can automatically detect the four corner nodes. For more complex structures, it can happen that the optimal corner nodes are not found. Manually entering the four corner nodes can lead to a better result, in this case.