Dude: I've been interested in Speed Silvers for some time, and can't help being curious. You find them too light by default? But isn't speed the whole idea? Why would you want them to be heavier? It seems like a contradiction, on the surface.
But maybe you want them to be heavier so you won't constantly be bottoming out on their shorter travel? Technically, traveling beyond actuation, and having to absorb the shock of bottoming, would reduce typing efficiency. I think that's why many fast typists strive to "skim" the keys, pressing just to actuation and no farther. In that way, your quest for heavier springs would make sense.
I'm a relatively fast typist myself, but prefer heavier switches (buckling springs, MX Greens). So before I'd seek a Silver board of my own, it'd be good to have some feedback, especially from someone in your position. Thanks!