it does NOT look too difficult to drive the loop, in fact, it doesn't even seem to need a lot of speed ( thanks Kim!)

That loop doesn't even look that difficult to engineer! Obviously the part that all the other loops I've seen before were missing, was the hub that equalized the force of the heavy car at speed pushing out from the inside of the loop

Brendan tells me that the Hot Wheels double loop at the 2012 X Games was engineered to mathematical specs which worked out the speed and  force on the suspension to get the right springs etc... and the math was that the driver would go 52 mph, and the force on the driver was up to 7 g's!

https://www.wired.com/2012/07/hot-wheels-double-dare-loop