Okay thanks, but for my purposes, just reversing edges manually as I need is probably the simplest solution.
My imported file is nothing other than a list of points. It contains no additional information about normals, or anything else geometric or topological.
The bottom line here I think its that Sketchup is made for making models of things that might really exist, physically, especially architecture. But I am using it to make models of objects from abstract math, and the intuitive flow of the program just isn’t that well suited to that. I am probably better off using Mathematica.