And there's more.
The strength of a single fork is usually 50% - 60% of the forklift rating when the load is lifted at its rated distance. At the tip of one fork it may be 20% - 25% of the forklift's rating because you're now at 2 times or more the rated distance (I'm talking about the fork strength). And if you put a hole through a tyne that is 10% - 20% of its width and 50% - 100% of its depth at that point, the stress raising effect of that hole will weaken the fork at that point by around 50%.
Hence the safe load may be as low as 5% - 10% of the forklift rating.
And of course if you are slinging the load (that is the load can swing back and forth) then the rating has to be reduced a further 20% to 4% - 8% of the forklift rating.
Hence a 5000 lb at 24" truck may be limited to 200 lb - 400 lb if a load is slung from a chain or hook attached thrugh a hole in a fork.
Much better to purchase a third party jib or hook attachment and have the combination rated. Because it in effect reinforces the forks to a degree, is supported by two forks, and no hole is required in a fork, the rating could be 4-5 times as high at the end of the forks - that is 800 lb - 2000 lb.