When I got my set of bars I first put the rear on, then took it for a spin with the front stock bar still on. 'Spin' was just about the right word! Very prone to oversteer. Entertaining for a little bit.

With both bars on the car corners very flat and very balanced - at the limit you can adjust between slight over and under steer with the throttle. Without the rear bar you will still have a car very prone to understeer. Which is of course safer and more predictable. Putting more cornering load on the rear tires will help[ you get around quicker though.

Another minor issue is that the rear sway will make that inside rear spin a little easier if you don't have an LSD (and not many people do on PV's).

Oh, and PS - I've repaired/reinforced 3 out of the 4 mounting points. But my car is a bit rusty underneath.
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I'm JohnMc, and I approved this message.