I WISH I could remember where I read that the four mains were somehow an advantage. It made sense too. I cannot remember for the LIFE of me where I saw it. I think it was also talking about how stout the block was whether aluminum or cast iron. I just cannot remember where I saw it.
That said, let me pose this question. How many slant six basements have you seen dumped? I've seen a couple of them with thrown rods. One was still running, but I've never seen one with the crank blown out of the bottom due to broken mains. Have you?