In the few weeks I've had SH5 & TWOS, I've mostly managed to avoid them pretty well.
Same tactics as you Jonass really, deep as poss, and quiet, then wait for them to move on.
All convoys I've attacked so far have been unescorted
There was one with 6 escorts but all of the merchants were small/medium freighters, also outside of my patrol zone, so I left them alone for the above reasons! Not worth the risk.
I've killed a few destroyers though! Most to add to tonnage on way home, and in self defence.
The first one I killed was after I'd sunk a merchant about 40 miles east of Grimsby. It came over to investigate at full speed and I had nowhere to hide in 40m of water, so i went to periscope depth and sank it with a magnetic detonator on fast speed when it was within 1km!
And again today actually, on my way out of Trondheim, I'd lined up a 90 degree normal shot on it in the dark, got a little to close, and as I went to periscope depth they heard my engines slowing to a stop! It turns straight for me at 36 kts search lights blazing, i fired off a quick magnetic detonator from 800 meters, and she couldn't avoid it.
She must have rose 10ft above the water on detonation, completely broke its back, snapped her clean in half!
Looked a bit like this: ��
Very, very lucky though as I was dead to rights and she'd just started pinging!
But yeah, mostly just try and stay quiet and hope they f*ck off lol!