It is impossible to shoot a CV from behind with a torp. The CV moves 1 mph slower than the torp, and even if you fire POINT BLANK from a PT boat dead astern of the CV, it takes 5-10 minutes for the torp to travel a relative distance of 200 yards.
Can't slow the CV down, it's not feasible in this game, but I think we seriously need to compensate for this by speeding up the torps' speed!