I still think that stacking ships together is a bad idea. One ship can sink the whole stack. In my last campaign as the HRE, I had about 81 ships (barques and caravels) and the Byz had a total of 43 ships (dromon, galleys and fire galleys). The command star distribution was about equal. I only attacked with about 60 of my ships. Although the AI ships were often stacked, none of mine were. I had 3 to 5 ships in a sea zone and launched multiple attacks against the stacks. I slaughtered the Byz navy in about 5 turns with fewer losses than what I inflicted. An advantage of one or two per sea zone is enough. The last attack was 5 separate caravels (speed 1) against a stack of 4 dromon (speed 4). I sank all of them with no losses. This implies that if the first attack wins, then the whole stack goes and that great speed can be overcome. I think that the greater movement radius of deep water ships gives a strategic advantage over coastal ships and I can beat them with massed attacks.