4 seater springs may serve you well. But they are symptom treaters
I see the problem as the very limited rear suspension movement that these cars have. Stiffer 4 seater springs is certainly one way to stopping the knocking that can occur from insufficient room.
I have a different perspective and see my ‘soft springs’ as a good thing. I believe softer springs give better comfort, allow better traction on a choppy road surface and their 135lbf/inch rate is a close match to the rate of my front spring giving a good overall balance to the car.
Progressive stops tackle the problem of limited movement by complimenting the leaf springs with a rising rate at the end of the suspension travel. Whilst preventing body contact they also reduce body movement/roll too. Another subtle advantage is that they absorb some of that horrible jiggly vertical axle energy and allows me to run my Rutherford AVO’s on the comfy setting.
