I looked at the research on lightning for an article I did on grounding and bonding so can toss 2 cents worth in (I am also an electrical engineer if that helps). If lightning wants to hit the ground, it is going to prefer the path that goes through your mast over one that doesn't assuming you are close to the charge. I don't think it is going to matter if it is grounded. Remember that lightning is different than your 12Volt circuits in that it can make air conductive. Assuming it hits the mast, there is the question of how it will get to the water. Absent wire rigging or bonding to a keel bolt, it is likely to find some wires for at least part of the trip. I know it isn't well understood but I would assume it will find a path through the hull at some point near the bottom of the mast. Probably sink the boat. My strategy is different when it comes to lightning as California is #50 in lightning strikes so there really isn't much of a chance of a strike, my mast is shorter than the boats around me, and I stay in the slip if there is a chance of lightning. The one thing I learned from the reading is don't bond your mast to your through hulls unless you want the strike to remove them. There was a strike that instantly sunk a "well bonded" boat which had all its through hulls removed by the strike.
In the process of this research, I did a calculation that showed that a strong hit would melt my rigging. My mast is wood so the rigging is the path. If it melts, so be it. I don't expect to be hit. I am more likely to die in traffic on the freeway.
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Allen