Hmmm...interesting, but difficult question, mates..
. Its hard for me to imagine how to do this, considering my present knowledge of the war in general.. It will be easy for me to state my hypotetical opinions about this, based on all the things i've learned trough the years, but putting myself into Dönitz' place... its to difficult for me..Of course, there is some things i would have changed due to what i know now, but i think Dönitz did whatever he could do, considering the limitations he had to operate under..
Good question, btw! Makes you think..