Good info on the diving procedures etc. I'm not really trying to affect anything about the actual diving routine however. My problem is, my best candidate visually for my Pitch mod currently has one unfortunate side effect that I have not yet been able to get rid of - for the first few minutes after surfacing, the boat tends to rise and fall with the waves in a narrow band that just happens to be where it sinks down just barely lower (by only 2 or 3 feet it seems) than the cut-off depth where the game sends the crew below, and then back up to where they come back up top. The net effect is that the crew keeps disappearing and re-appearing 2 or 3 times a minute for the first few minutes.
The really frustrating part is that this only occurs right after surfacing - they stay up there just fine after a few minutes, once the boat picks up speed. If I could just drop the "crew goes below" depth by about 4-5 feet, without changing the boat's actual dynamics, it would solve this problem. As DTB points out, the surface draught value (which is the one I was referring to in my second post above) does affect this depth but it also screws up the boat's behavior too substantially to be a workable fix for this particular problem
It's really great that the devs gave us so many things to play around with - it's just too bad that so many of them seem to be multi-purpose things that affect several functions so it's hard to hone in on making the particular change (and only the particular change) that you really want to make.