Scott,

I think Toby's post is instructive. The result of a direct hit is going to put holes in things, and with millions of volts, most surfaces on a boat are conductive. All that power is seeking a ground point, wherever it can find it.

My guess, based on Valhalla is that the through-hulls were to serve as ground discharege points. I have left the through hulls connected for this reason. The code requirements are for a minimum of 1 sq ft of surface area (copper plate) for the discharge point. I don't believe that the spongey sintered copper rf grounds are sufficient. Again, I have heard stories that boats have been damaged because they used one of these rf ground plates. The story goes that because they are essentially filled with water, when they discharge a lighning stroke, the water is immediately turned to steam and the plate is blown off the boat. This story is probably apocryphal, but the code requirement is for a plate ground.

I have never seen an corrosion on my rudder post, so I have not worried about that. I don't know if the pins on the shoe penetrate into the keel void. If the zinc on your rudder is not wired to something or connected to the lateral rods in your rudder, then they are just weights. I have not been completely under the cockpit floor so I don't know if the rudder post is connected to the ground system. If it is not, then you do not have a protective system for the rudder. There is not a return connection to ground.