I've made contact with a nautical archaeologist based in Turkey who has done an extensive reconstruction of a ninth century sailing vessel on which my Venetians' ship is based. I have a whole list of questions on sailing and cargo characteristics for him: so I'm very excited to have gotten a reply and also some references for commerce at that time. You'll notice from the fact check list that a lot of the details are in specific prices and relative values. Also the technical information on sailing characteristics will be very helpful in the action scenes.
Sure, sure, the casual reader doesn't know a tack from a clew and doesn't care. But I find that the best part about reading good historical fiction is immersion in the culture and technology, even if it's not understood as long as it's self-consistent.