[Curt]

Since first starting this thread I've gone from the original setup on the 08 FA5 I recently purchased (stock suspension with H&R springs), put in the HFP dampers and springs plus the Eibach rear sway bar on the softer of the two settings. Huge improvement. Just today I put the rear sway bar to the stiffer of the two settings, and like the handling a bunch better.
So here's the question: Discounting all of the analytical discussion about the sway bar diameters, configuration and moment arms, in a relative sense where does the Eibach (in each of its 2 settings) stand in terms of stiffness compared to the stock Si bar, the Progress bar and other rear sway bar options? More specifically for my curiosity, is the Progress stiffer than the Eibach (on its stiffer setting), and if so, by about what percentage.