Tethercar revival

Diminutive model race cars were achieving speeds of 100+ miles per hour.
They were, as the name suiggests, conected by a strong cable to a tether post in the centre of a flat smooth area of concrete or similar.
The cars' engines were started and they were launched to run in the circle whose diameter was constrained by the length of the tethering cable/wire.
They exist to this day - mainly highly engineered with specially milled gears and high-revving engines (usuall about 5 to 10 cubic centimeters capacity)
This was all very well, but the cars required special, costly engineering and their tough streamlined bodies had to be carefully made to fit.
Home-made cars didn't stand a chance in competition, but hobbyists still built tethercars of their own design, with limited