Most likely it could be stress fractures on old welds along hulls that would fail to cause oil spills... Wouldn't matter about # of hulls... Engineers with more knowledge than most help set guidelines... Common sense leads most to know that over time, old stuff starts to fail somewhere... Dolphins are worth keeping safe... If a vessel is sailing up the East coast to offload in a Canada port, does anyone check the hull size?... https://www.marineinsight.com/shipping-news/aging-shadow-fleet-loaded-with-russian-oil-poses-risk/ Time for the East Coast fishermen who were attacked by environmentalists to highlight their real lack of effort to protect ocean waters... So we watch...LJ