Finally beat el impoluto :)
What I did was just play aggresive, during the opening animation of it charging for you, fire a mortar right in front of it so it runs into it and fire some chain shots so it slows down and hit it with a ram of your own, immediately broadside it before It does its 2 foot charge (it can and will do it) as to deal some major damage to it before it gets you. It'll start running away and trying to regroup itself so don't give it that chance, brace on the cannon fire, fire back with your own and mortar it/chainshot it to death. Its ok if you take major damage, it got me down to my last sliver of health lol. Full upgrades are a must except for fire barrels.
As much as I like reading of your endeavors against legendary ships, perhaps it would be best to condense it all in one thread.