Well, what can I say. Obviously, different men are of different height, so, some will be able to peer over the top edge of the bridge more or less easily than others. My guess is, that a man about 6ft tall and not elevated by any means, could just peer over the edge of the bridge, of a type IX-boat.
(Another image of U-126)
Unfortunetly, I am not a modder or graphic designer and can therefore, not contibute anything to that part of the discussion but in my estimation, the bridge would have to be enlarged or at least the top edge of the bridge has to be raised - in my view, the type VII-boat and bridge is well proportioned in SH3.