[simne]

> slower on the surface than most naval vessels of the time

That is point. I'm not agree about most, but will be agree if you say about many.

> they couldn’t outrun pursuing destroyers or corvettes

But problem was, navy have so huge deficit of ships, so some convoys was run without naval support.

Sure, if all convoys was supported with fastest ships with best commands, u-boats will be no problem anymore, and as I understand, once this was happen.