Hi Tim, I have to disagree with you on the spring back bit. I did one wrong and it did spring back, but during the over heads and in the four leaf and gave me fits until I realized what I did wrong. The TE inside the fuselage, as stated else where, is in fact a straight line TE so there is no spring back, just free controls.
I know that you and Robert have both said this, but if there are two distinct hinge lines then there is going to be a need for flex that will have to be absorbed someplace. Maybe with a rigid assembly the flex and the springback is slight enough to not be noticeable, but unless all the hinges are on the exact same line, there is going to be geometry-induced flex, and hence geometry-induced spring. Sanding a flat in the TE where the horn affixes won't obviate the need for flex, but it will certainly make the controls smoother.
Perhaps the terminology problem is that you're speaking English and I'm speaking Engineer, where anyone who's been in the biz for any length of time knows that there is no "perfect". There is only "good enough" and "not good enough", and often "detectable" and "undetectable", but perfection is just a dangerous illusion that makes you spend money on unproven technology that bites you after you've spent a bunch of money and now need to ship a product with deep built-in problems. Moreover, most engineers have been in situations where someone is insisting "no! it is perfect!" about a part that ends up being a source of very expensive problems.
So engineers don't use the words "perfect" or "none" without qualification unless they are quite aware that they are speaking hypothetically, engaging in hyperbole, or are outright dreaming.
I'm perfectly willing to believe that you have built wings with swept trailing edges and no
detectable spring-back, that had an effect on the airplane performance that was not apparent given the magnitude of all the other forces involved. But you can't sweep a TE, rigidly affix a horn to your two flaps, and not have
some springback, however thoroughly you might fail to notice it, or however thoroughly it may fail to affect the flight of your plane.