Allow setting of fitresult. Currently, fitresult is left deliberately hidden by creating a new variable here with the same name. This should be fixed but it causes different behaviour which breaks several unit tests. The issue to deal with this is #13950. Other related issues are #13667, #15978 and #19773.
This needs to be completed to deal with apex points In the case of a apex (e.g. top of a pyramid) you need to interate over all clusters of points on the Snorm ie. sum of 2, sum of 3 sum of 4. etc. to be certain to get a correct normal test.