Don't worry about achilles length, as your not going to lengthen it.
What you can do is improve the passive stiffness of your muscles, stiffen your tendons, strengthen opposing muscle groups for stability, and improve your ability to store and express explosive power.
Thats what this work is about.
There have been atheletes that break the mold that have achieved the vertical and speed that many are looking for.
Oh, it would also be good to add power cleans.
Make sure you drink a shake and amino acids after your session.