This is my experience also (GWX). I like to play 1945 campaigns sometimes, but find that once I get a Hunter Killer or escort group on me I'm finished. Of course, by that year they can ping you well below your crush depth so there's not really much point in going deep other than for evasive manouvering.
The Bolds do help a bit. I usually eject one after a depth charge run when I'm making a big manuever. In doing so I'll go ahead flank and dive, trying to build up as much speed as possible, so that when I go back to ahead slow I still have plenty of momentum to coast as far as possible. Also a slight course change of about 30 degrees - no more because it causes too much drag. My goal is to try to get out of their circle of immediate detection, but I've never made it yet that late in the war. Once they've found me again, I'll climb back up in preparation for my next chance. I play with map updates off, so I always have very limited information and situational awareness.
I have also adjusted the asdic min surface values in my install somewhat like Stiebler/NYGM, so that the profile of the boat has an effect of how effective their asdic is depending on the angle. This is quite fun to play with earlier in the war as you can avoid diving deep to evade and mess with them to an extent. But late war it's next to useless I find.
So yes, I find the Bolds useful to distract them for a bit, maybe a minute or so, but then they find you again. Depth, silent running, profile, all never seems to make much difference in late war. Still fun though and I appreciate the challenge. Maybe one day I'll learn the secret.
