A few new ideas

[Fidd]

I don't doubt the veracity of what you're saying, but from what I've seen - an image of a merchantman clock with the periphery marked for when zigs should be made; it makes we wonder if we're both right, namely that there were short-interval zigs to make solutions more difficult when under fire, and longer interval ones designed to frustrate establishing the convoy's base course, as you describe.

In other words, we may both be right.