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Amazing work!! I have been thinking of this exact project for some tube stock I have left over. I see you have been asked over and over about the pipe sizing so I won't go there but I'm very sure I don't have the exact size. I am willing to scale up to the nearest tube I have and report my results. I see most of the frame should work with that technique but the middle looks complex. Which is the best part or assembly to print for a test?