Using TMO and RSRD with a realism setting of 90 I think....just got the external camera on. Have to admit the destroyers here seem a bit dumb.
One of the three broke off and headed back to the main group and, luckily for me came right over my head on the exact same course. Thank you skipper

Flank speed and follow her in
Ok I couldnt keep up but I managed to get all the way in without any of them spotting me. Up scope, troop ship sunk and damaged a large merchant. DIVE DIVE and thats where I am at the mo.....will hopefully finish off the rest later today.
Going to have to try and sort out this manual targeting so that I can use the aft torps better, currently I am using the Dick' OCane way and its a right pain having to swing the boat road to get into position especially when up close.