I think that it's fairly common that the drives are lightly loaded. If 85# is the lowest on the scale, then that's the minimum I would run. Personally, I would probably bump it a bit to 90 or 95 pounds. I don't think you can hurt anything at those values.

In looking at my last weights, mine too is off the charts at the bottom end. I'm running 100 pounds in mine, instead of 85.

ray