The following diagram explains the difference between the ‘Envelope Normal’ and the ‘Wheighted Facet Average’ option; obviously things have been exaggerated here to show what’s going on. Within the envelope are two imaginary struts, which meet at the zenith. The cyan line shows the envelope normal Ne. The yellow line shows the weighted facet average normal Nw of the faces surounding the hub. Only the weighted facet average normal passes though the axial centre of the struts; and this yellow line marks the mitre for cutting so that both surfaces meet. The intention here, is that Nw passes through the axial center of all forces meeting at the hub.
Note: The envelope normals for concave superellipsoids are not always not well defined at the edges; so if using concave shapes please leave the hub normal option to ‘Auto’ as this will give the best results. I have deliberately avoided limiting the minimum exponent values to 2, which means concave shapes are allowed.