Interesting point about the map markings,I have actually considered that before,but decided it was highly unlikely as the game SHOULD be well enough designed to allow players to make as many markings as they like
For me,when normally leaving French waters I draw my usual RAF markings around UK and Gib.,so I have a rough idea of when I am leaving the danger zone and able to sail surfaced from then on.I also draw a ring around F.Town if I am sailing down those parts.What I also do,is before a new patrol sum up all the expected activity in the area and the most favourable lane for me to stalk/attack,and concentrate on that lane,I do this by plotting as near accurately as possible the merchant/convoy lane as indicated on the map that came with game,So,in my current patrol in EE65 I noticed there is a huge convergance of activity around the Canary islands,and I used that area to focus the beginning of my final leg towards my PZ,and sailed along the single merchant route inbound to Gib.Being able to actually draw the merchant line on the map and sail along it is a useful tactic for me,putting me on a rough collision course with any merchants heading my way.
So in conclusion,it would be better for me to erase all the RAF markings for example as I pass them,and just re draw them as I return?.Damn,this really is unfortunate,as the markings can also be used to remind us of important areas/events for example.I really dont want to lose my lane markers
Anyway,thanks for the input,I will erase some of my markings later,and see what happens.