One article says the Rusky engineers even copied patches on the B-29 that they knew were patches just so Uncle Joe wouldn't get mad at them for not obeying his order to copy it to the last rivet. One of the problems in the Tupolev TU 4 version was the Ruskies used metric guaged aluminum for their copies, which was thicker, so their planes weighed more and thus had less of a payload. But it could reach Chicago on a oneway suicide nuke trip, so the Pentagon thought at the time.