If the pin box on your trailer is a Goose Box you may want to rethink about changing it out. Many people tow with and swear by them. If a Goose Box, it already has air damping included.
Air style pin boxes work pretty well for lighter trailers with less pin weight. On heavier trailers the bladder has to be pumped up so hard they lose some effectiveness. A main issue is the pin box goes with the trailer should you decide to upgrade.
If you have a goose neck adapter bolted to a standard pin box then you would be better advised to revert the pin box to standard and use an air hitch. The damping performance would be superior and you could use it with your next trailer if neccessary.