This is a really interesting read for me. I've just recently figured out that if I'm a perfect 90deg AOB on a convoy and I have their speed then the distances are irrelevant*. Until now I've always attacked submerged, as close to the convoy as possible but I'm going to start trying some surface attacks from a distance armed with my new found knowledge.
I'll report any findings Banryu
* I normally spent Maths periods hiding on the golf course next to my secondary school.