How to start with a Type IXD2 in 1939?

Most uncharitable, Sir! I have given myself a handicap: the IXD2 is slow to dive and unwieldy in maneuvering especially when submerged. Not to mention that its size (should in theory at least) make it more visible to the enemy. With a green crew, moving at 1/3 ahead, I counted a bit over 60 seconds to get to periscope depth from surface running. Can I expect this to get better over time as my crew become more experienced, or does the game not model that?

Related but as an aside, U.S. submarines were more literally diesel electric, with the diesels permanently attached to electric generators. Even on the surface, electric motors were turning the props. I wonder if this might make diving more rapid . . . that is, in a German submarine I see a period of time where forward momentum is rapidly slowing down because the props aren't spinning during the transition from direct-drive diesel, to electric propulsion. This loss of momentum reduces the effectiveness of the diving planes and should increase the amount of time it takes to dive. Does anyone have further thoughts on this? How much fuel efficiency loss was there in the conversion of mechanical energy to electrical? If I recall correctly, in this era, we're looking at perhaps a 10% loss but I could be wrong.