On several occations when my position was ahead and on the path of the convoy, I went to 25-40 m, turned my boat so it faced the convoy for a smallest possible porfile to reduce chance of asdic detection, and set speed at 1 or 2 knott.
Then, after the escort passed by I ordered PD and turned my boat so it's as close as possible to perpendicular to the convoy's path.
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xlbob
GWX v 2 
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