I agree that before I do anything, I have to select a U-Boat. THat is probably going to be u-96, unless u-99 has a cool emblem too. I agree with you that if I do this at all, I should either choose play 2b or 2c. I think plan 2c would be the easist. Just fill one of the rows, then lower the second torpedo tube a little. Anyhow, #2a is pretty muich out. In addition to the slippage issue, the putty wont hold up against that large of an area.
I may not have to do this at all. But since the U boat I am leaning towards most is Type VII C, will probably have to do this. That is why I am thinking about it now.

Best Wishes,

Einsamer Wolf