I have a 16' Procraft bass (crappie) boat and changed out the two 6 gal fuel cells for an 18 gallon cell and went with a four battery setup (lights, trolling, etc) after doing so the boat had a hard time getting on plane with a 60hp merc. The sting ray made a world of difference!!! The nose never even rises now it just gets up and is gone. Went from 36mph to 44mph just by bolting it on. Adjusting the trim also adjusts the height of the bow, rough water is much easier to handle.
There are a lot of nay sayers on here concerning hydrofoils, but for my situation it is outstanding!!! If your boat planes out quickly and maneuvers well, it probably won't change things much, but if there is any doubt I would definately recommend one.