Explain this.

I'm not sure how much you would feel. Like they said - it adds lift, and it quickens the rate of lift and closure (because it moves further in the same number of crankshaft degrees). It will give you a more consistent racker ratio, and you will get more stability because they won't flex. So you might see more rpm depending how bad thigns are now. You also are asking more of your valve springs (because the ratio change works against them) and you make have geometry problems depending on what heads you have and whose rockers you settle on. It's a big chunk of coin IMO if you don't already need them.