If anybody is interested, it would be great to have the odometer log that was in the tower of the boats. Picture below from U-505, and the VIIs had the same.
The top counter shows nautical miles traveled, with a zeroing knob to the left. The bottom counter allows the user to preset a certain number of nautical miles with the knob at the left. A signal would go off when that reached zero.
I’m not sure how feasible, however it doesn’t need to be the device itself modded, just simply a resettable odometer in some fashion. I don’t know the first thing about how to do it, but if anybody has the skill and interest….
Thoughts?