but I think there's a house rule which states that the bigger ship prevails... masters?
I thought I saw something like that written somewhere sometime, but I didn't see it in the written rules. Perhaps the bigger ship rule was mentioned in a previous forum thread. If the bigger ship rule isn't just a figment of our imaginations and is the house rule, then in this particular case, the 20-ton ship moved into the hex while the 18-ton ship got the life raked out of it. Either way, ouch.