first, you can get a job working fo NASA, doing the math for the Mars missions, with that conversion from 1600k, (one too many zeros?)
second, you don't tell us which model or series of "cat" tele-handler you were using, and there is a real possibility their may have been some "down-rating" where you can only lift a weight only so high and so far out before you have to "de-rate" the capacity of the machine, and lastly, you are correct, it is possible to be on such an unstable surface as to make lifting a less than capacity load unsafe