X2
Sultan, I can imagine that the " Spirit of Rett" racing team operates with the same enthusiasm and technical energy as the X2 team, and while I might not be able to agree that it is a more impressive achievement than the X2 due to my inescapable bias, it is a terrific feat. And all the more so when I read that their Chevy engine doesn't have a blower; it is naturally aspirated!
Dave Jackson, it appears that the X2 can do nothing to impress you, and that's too bad, because the only thing it shares with the XH-59 is that it has a contra-rotating main rotor. It couldn't have been built at the conclusion of the preceding ABC as "the stuff" that goes into it wasn't available.
Thanks,
John Dixson