[CB..]

if one could find the graphic file for the view angle (the yellow view cone) on the compass and replace it or add a thin centre line ..then you could use the compass to guestimate the view angle (at least as accurately as you can set the torpedo angle anyway..given the crude AOB gizmoe)

other than that you can see the bow of the sub as you surface or decrease the depth so you can get 12 degrees of the bow by setting the scope extreme edge on the tip of the bow..at relatively close range the ship itself is large enough in the scope for the centre of the ship to be 2 or 3 degrees "behind" the bow of the ship..so there's 15 degrees if you fire the instant the bow comes into view etc etc ....really it is a case of using all the possible bits and bobs of information you can gather adding a bit of practice and experience to the mix and improving your guestimate untill it is reliable...part of the fun in a way