Ed was correct
I had a 1980 H30 for many years but I could not find any photos of the skeg and rudder. Ed is correct, there was a flat metal plate attached to the bottom of the skeg, that extended aft about 8-10". It had a hole in it that fit the stainless rod on the bottom forward end of the rudder. The plate did not seem to support much of the vertical weight of the rudder while the boat was in the water, since the rudder floated up and rubbed somewhat against the hull around the rudder post. It had to be strong enough, however, to resist the lateral and twisting forces on the rudder. Perhaps you could call the technical folks at Hunter Marine and ask if anyone has any specifications for the skeg, plate and rudder.