I used to work for Pirelli cables pulling in phone cables for BT, iwas the winchman had a hydraulic winch run of a Ford4x4 County tractor , we used Dyneema synthetic rope to pull in the cables 1500 meters at a time the cable was 30ml dia and had a dead wieght of 4.8 tons , to get the rope under tension would get the front wheels of the county off the ground before picking up the cable , now what all that equates to in terms of tensionxwieght etc i dont know , what i do know is that in 11yrs of useing dyneema rope never had one break had total confidence in its ability to do the job, the rope was supplied by a chandlers yard in southamton - i use it for a tow rope 1/2 inch its taken real abuse over 10yrs or more. go for synthetic and treat with care -will last a lifetime.