the only ski's i have ever had to shim were on my old '96 xt 600. currently i have an '04 warrior with usi's and have no problem . my wife has a rage with stock yammy's on it and no darting! she is going to go with slydog's only for the boondocking, otherwise would keep the stock ski's on.
i have heard and read good things about all ski's. i would say pick your favorite and go with it! if it does dart , tighten your front limiter strap 1 notch and go from there. don't even worry about shims!