Re: problems after planing
Your boat was designed by naval architects and built in a time when boats were boats. Hydrafoils and trim tabs are for the boats they make today and are often needed to correct basic deficiencies in the design. Your boat / motor combination should run perfect without them and adding them will not help you.
I would suspect that the hull has a rocker. If it had a hook it would probably just porpoise. In either case, though, the whole hull is probably hogged due to dry rot and / or improper placement on the trailler. It may look "flat", but to truly evaluate it you need to look very close.
Put a long straight edge down the keel. Raise the motor to get clearance, then look down the keel and check for symmetry on both sides of the keel. Repeat by looking from the stem. Lastly, check that the engine is centered on the transom and perpendicular to the bottom.
Finally, if you have cable-pulley steering, check to be sure the cable is tight. Both sides should have a spring at the end of the cable, and it should have tension on it. If either end is loose, the engine torque is turning the motor by itself.
