Instead of raiding Loch Ewe, plot a course inline with the northern coast of mainland Scotland and Stornoway. I've sunk over 6 large tankers in that area and they are only escorted by an Armed Tug Boat! You also get a convoy coming through past Stornoway which is easily dealt with.
I'm using GWX 1.03 currently in August 1940. Type VIIC.
Hope this is of some help.
