dont look at them as rock sliders, look at them as jackable sills. doubt you will have much call for sliding over rocks or infact fending off trees. BUT they are very very handy to use as a jacking point. just slip the Hi lift under it and stack it up!
when you say steps, i presume you mean, fitting them AS WELL AS the sills? not sure how they mount but as ratty says tree sliders can also double up as a step.
G