I think the C-17 is a bench mark goal. Its what the Y-20 wanted to be but with the technology available only allowed for Antoniev or Illusion or any ex USSR company to join the bidding. I don't think they got the machinery from the states. However, I do suspect commercial companies involved native to China. Its better than starting the same assembly line of anything on market, just improve it. Its built on proven aircraft/fuselage, and that for certain. Also the engine, will be an incredible challenge that will prove the success of the aircraft. Since the PLA isn't transparent, time will tell of its success or short comings.