Couple of questions
 

In SH4, how do you attack a couple of ships heading in a straight line?? Whereas the TDC in SH3 automatically corrected target information when you turned your optics to a new ship in convoy, am I right that SH4 does not do that??

When you want to fire at the second ship, do you have to lock the scope onto it and then resend the range and bearing to the TDC??

Cheers :)

yes, you're right about fleet boats not updating the bearing. So if you want to attack a second ship in a convoy you'll have to reinput everything except speed.
Alternatively, if you just want to shoot for example 20 degrees left of your current solution you can turn the spread dial to 20º left.