One could just load the boat with all MK10s until after about August 1943. May not be entirely realistic, but neither is compensating for the 11ft depth difference, which is too big a temptation for me. They are available to use whenever in port at no charge and you will encounter a lot fewer duds. Or, start with an old S Boat. Limited range, limited depth, limited speed, batteries that take forever to charge, no aft tubes, no aa gun, BUT, they came with MK10s. In RL that is all the S Boats used. After a frustrating day at work I want to be able to sink some ships not continue to be frustrated.
Using TMO 2.1 (love it!)
, NavMap Update (love it!)
and 3 or 4 other minor tweaks that are more to my liking.