Hi Richard
I found a parts web page from Aero Racing which shows the rear brake assembly. I think it covers the new Plus4s although it doesn’t explicitly say so. If it is correct then the hand brake consists of two pads clamping on to the actual disk using a cable assembly. I suspect this this method does not work on steeper slopes as it cannot provide enough friction to hold the car. If it had been a hydraulic assembly like the foot brake then it might work.
Andrew
