I will print the rear dropouts in plastic first as a proof of principle. I am curious about attaching the stays. All of the videos I have seen have the straight slots cut into the stays. But then I never see how the builder bends the stays. If they go in straight, that would require to bend the stays. On the other hand, if you angle your slot cut, the stays can remain straight. Is one method prefered over the other? And then why is that?
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David Kirk created a dropout that has a ball on the end...it fits into the tube like a ball and socket joint
I couldn't find s simple picture on his site but you can see it on the table of parts and in build mode here
Build | Kirk Frameworks
it might be something you could do in similar manner