They need to also subtract the weight of the feet being nailed and likely the heels only barely on a tiny protrusion of wood to keep them from falling free of the cross so the weight likely would be half. Also men were incredibly more robust and solid then their tendons and muscles built with real food not todays pig waste processed food but natural food would make the body more able to hold together and if you've tried to cut meat apart then tendons and ligaments are tough as fuck like mens bodies of the past were. I think we fully underestimate our forefathers power and strength, they were mighty then unlike us pussy/weaklings you were mighty or you were dead, no guns or other equalizers then.