HopCar,the sky car was before my time,but I know a bit about it.
The truth is it isn't rocket science to build a large multi copter (aka drone) these days. You can by the boards to make your own. If I wanted, I could have a flying model like that built in weeks out of foam and carbon fiber. But it won't have any payload to speak of.
If you're interested, go take a look at what Peter Siripol sp? made while he was at flight test on YouTube. He's even started his second electric
ultralight on his own channel.
The real money
is in unmanned aircraft for things like agricultural spraying and let's face it. If DGI and other big companies with huge budgets and industry connections can't make it happen. Then I doubt this guy has found a way to increase the payloads .
We are close to reality but battery tech is holding us back still.