I am using surface cut to create freehand polygonial selection. Then, I go an convert this segment to a model to measure its area. However, reported area is twice as large than I expect, since it is also calculating the area behind (I think).
Is there away to configure surface cut to select only the external vertices?
Yes, if you want to compute area of a 2D polygon then you need to divide the reported 3D surface by 2.
Among the new markups widgets (that is planned to be released early next week) there is a “closed curve” type and for that we will report 2D area (so you won’t need to divide by 2).