Accuracy perspective: Years ago before current modern sailplane airfoils and computer modeling of wings, a group of people were wind tunnel testing an airfoil. Somebody stuck a piece of Scotch tape on the upper surface, and drag dropped 30%.
Practical perspective: The hinge line for flaps and ailerons must be straight. I stuck a straight-edge (one of those fancy ones) on the hinge line, and tried to stick a feeler gauge under it and no go.
If I am pushing the envelope with the MPCNC, then I am probably pushing the envelope with manufacturers of internationally competitive almost ready to fly sailplanes. I know of nobody that sells them who guarantees or even lists any degree of conformance with the airfoils they supposedly used. The real “accuracy” test is whether or not it wins contests. In all likelihood, the airfoils used are those designed with a computer modeling program, scaled to length of the chord, and then machined with a CNC router (all sorts used but generally higher end). CAn you say expensive? What sells it is the designer of the airfoils (no guarantee the buyer actually got that airfoil series), the weight, and any track record of contest wins. Or for some buyers, so and so uses it. It’s just like few golfers benefit from a $1000 driver.
All molds get post-sanded. The real desire is after coating with auto paint basecoat and clear coat, does the resulting wing exhibit a mirror finish? It gives an illusion of low drag. Never mind some will put turbulators (fancy Scotch tape) on the wing.
It would be cool to win a big contest with a plane made from a CNC router that most any modeler could buy. I suppose that’s my real objective.
Hopefully, you can now see why I am pushing. Apologies in advance.