I had a 3.5 m with a 25 hp, 2ST, with tiller, and I fitted it with a hydrofoil. The result was impressive, specially when towing rings or knee-boards. It started and went into plane much faster.
I moved to a 4.5 m with a 40 hp, 2 ST, joker seat and when I fitted it with an hydrofoil the result was also impressive. Without the hydrofoil it was hard to pull a skier out of the water being alone in the boat and with no extra weight in the bow.
Now I have a 5.2 m with a 90 hp, 4ST, standing drive position, close to the stern. The result is similar. With the hydrofoil the bow stays low when starting and boat starts planning immediately. Planning speed is also reduced. The only con I found is that starting in a tight turn with the trim low has some strange results (difficult to get it straight).