Losing crew to other boats

I am using SH3 Commander but don't like the option where it transfers out one crewman after each patrol. Not that I'm against the realism part, just that I don't like that if I go into SH3 Commander later for something (like to rename someone) it then will take out another crewmember. Plus, I don't think losing one crew per patrol is historically accurate.

So I wondered if anyone had done research to know about how many crewmen were transferred to new crews or new posts after a typical patrol. I have read several books but never tried to glean much direct info from them. I was thinking maybe I could start transferring out crew myself (dismissing them based on a random die roll). My first thought was 5% among everyone except the LI, IWO, and IIWO.

So on completion of a typical patrol any given boat would lose about 2 men. Does that sound typical? Or should it be a little higher, like maybe 10%? Thoughts?

And what about the LI, IWO, and IIWO? I know lots of times an IWO would serve for a while then go to command school to get his own boat and the IIWO would mostly be promoted to IWO. How many patrols was that, typically? Maybe three? Again, I'm just trying to get my crew to more or less follow actual Ubootwaffe history.

What about the LI? I don't see where they seem to get transferred out too much. Are LIs more or less tied to the boat, so that they know them intimately and remain fixed to a given boat?

And lastly, what about the captain? In the game you can get yourself a new boat. In real life, if a captain took on a new boat, he didn't bring his old crew with him, did he? Again, just looking to get some information from this informed community so I can make my own little rule set on the side to keep my crews in line with historical actuality.

Thanks.