In the previous part 2 installment, TWO (2) hazards were discussed when trying to re-use the floating head line weight class for a sinking head. The Active-Line load appears to be a more telling story than the standardized effect of weight class. This part 3 installment is to explore what is behind Mystery door #3, an unpredictability we were left with from only having casted the unmodified final head in part 2. We will be chopping and assembling this unmodified head to get all 9 digits of the line matching zip code for that Zpey - or any other - rod. This is akin to getting both the right shoe length AND width size. At the end of this part 3, we will see behind door # 3 awaits some nice surprises, along with those that will make us ponder further depending on how far we want to go down the rabbit hole. Just as when we feel we are getting close to mastery, we are humbled when we simply end up as a better student.