Dragonfly - the horizontal pulling capacity that the truck has is of little to no consequence with respect to the wisdom of ahitch extension. It is the vertical load that the tongue of the trailer imparts to the drawbar of the hitch that is the problem.
By extending the point through which this dynamic vertical load acts further away, you are increasing the level arm and hence causing more twist on the hitch and and truck structure. How much depends on many things. Unless proper calculations are performed this idea is not a good one.