What about 2 stage springs? I don't know much at all about suspension, but read that most sport bikes come with these. I don't know what HD comes with stock. It looks like the HD lowering springs are two stage. (This is regarding front springs. I don't know at all about the rear shocks.)

 

Interesting post. I have Progressive 442's on my Sportster and they ride much different than the stock shocks. I know everyone love's their Progressives and I will say that the Progressives handle much better than the stock shocks, but the stock shocks we're more plush and cushy, which to me makes for a more comfortable ride. As far as safety is concerned, the Progressive's feel a bit more responsive and stable. Just my .02.