I'm only on my third patrol, but I'll try to answer the first part of your question. In the sub I'm sailing, a VIIB, the fully submerged depth seems to be around 10-12 meters with peri retracted.
That's in good weather, though. Have never really worried too much about it in rough weather, even though the troughs between waves often break over the con. Future patrols might make me feel a bit more apprehensive about it, though.
