I would not change those springs at all. Any of the Robart struts that I have ever had are too soft, if anything. I know that you may feel that it is too stiff a spring when your plane is sitting in 1 G on your work bench, but in a landing gone awry, you want STIFF! A 19 pound Roo hitting the deck, even on a medium landing, is gonna compress and bottom out those struts. I've been looking for springs to make them stiffer, not wimpier.