Hawk...
I have found thru extensive trial and error...every DD they can throw at you goes down on one shot set at 3...mag is best. Every damned time.
I deliberately get their attention about 1800 meters out...run loud and noisy on the surface, go to PD, let em' close...really close...at about 500 meters straight on...give 'em an eel. All gone.
If you miss....you'd better express it at flank to hells gates while turning hardover. It does take some practice!
I also rigged the boat for one patrol with T5 acoustic eels(tweak program)..we're talking seriously unfair to the DD's here! Fire and forget...from as far out as 4000m.
I went back to the T2's and steamer mix until later.