1kts is correct....it helped me escaping a DD, who kept on chasing me long after the convoy continued it's course.
You can try 2kts, and if you're using the stealth-meter, you can see whether it's safe to do so.
It wasn't, in my case. :p
I went to 245m, and manned the hydrophone myself.
I kept on changing our course, to keep him at our stern (=smallest profile, while still sneaking away, allthough it's on a very low speed).
When I heard him dumping depthcharges - and revving up his engines - I increased speed to 3kts, made a hook to L or R, and went back to 1kts...eventually changing depth by 20-40m as well.
After 3hrs - all in realtime - I had managed to loose him.
