First, it was only two destroyers. If I said 3, I was mistaken.
What are your evasion strategies like?
Like I said, the weather was crappy and the sea state was high which works in your favor as the DDs have a harder time hearing you in high seas. I had about 60 meters to play with. Secondly, I have had a lot of experience evading elite escrots in SH4 using the Triggur Maru mod. Try it sometime. It's scary.
This is my strategy when detected and the DDs are approaching.
1. Crash dive and order full right or left rudder (doesn't matter)
2. straighten out my course and order ahead slow (1) + silent running
3. Usually at this point they have come back around for another DC attack. When your soundman calls out "Wasserbomen" order ahead flank and make another drastic course change. After about 10 seconds stop engines and coast. You should be fairly deep at this point. 100m if possible
4. At this point, I monitor my sonar contacts and when the DDs are moving away and their stern is facing me, I go ahead slow for short periods of time. As soon as one of the DDs begins to come back around (when I hear "warship constant distance") I cut engines again. (I still use sonar contact lines because I believe it simulates the help you would get from your sonarman)
5. Repeat step 4 until you've gotten away from the original position. If you've done everything right, the DDs will be looking for you where they think you are (usually where you dove) and not where you are. As the distance between you and the DDs gets greater you can order higher speeds and still remain undetected.
I suppose its possible that I overwrote the IRAI files with another mod but I don't think so. You helped me get my mod order correct

so I'm pretty confident it is right. I'll check when I get home tonight and post it.