Thanks for the response! I have noticed that some corrections are made by the helm i.e. when lying "at drift" there will be minor rudder corrections, but since the map doesn't display currents and tidal flows it's impossible to acertain if they are correct adjustments or just "dummy corrections".
Having some information on current/tide on the map, would really make for some interesting tactical situations. For example, between ALDERNAY (northern most of the British Channel Isles) and the French Coast you have a tidal current of up to 9 knts ("The Aldernay Race") - imagine using such a current as your exit strategy ... on the surface the sub could be doing 30 knts. ... no more creeping out with 1 knts. - of course you would have to make sure the DD's are facing the current
The lack of data provided really annoys me ... for example, when doing 90 degree rudder it looks like boat speed is the same as with rudder amidships - I always use less rudder to ensure that I make some way across ground on low speed, but I'm uncertain if it has any effect.