C4U = Not worth it. The enlarged end of the spring doesn't fit well and so the spring barely compresses like it should.Has anyone put c4u springs into a SS5x5? I florian modded mine and I'm getting some screw and spring sets from c4u soon. I've heard different opinions on using dayan springs but c4u I haven't found anything on the subject. Did anyone try it out? If not, I will and I'll post about it.
Also, dayan springs don't work very well in my experience, they're too soft and so they reduce the springy feel of the cube too much. It wont cut corners.
Give it a try by all means, you never know how good it could turn out (no pun intended). I find with the new SS 5x5s it isn't even necessary to change hardware...florian mod will suffice.