Stone of Destiny using and sub class with the same race?

Hi all,
I'm Maestro Tyr warrior in main class lv87. Can I sub to Warlord (Dreadnought), and go 4th? Or can I use Stone of Destiny to change my Maestro Tyr warrior to Dreadnought Tyr warrior and stand inlv87?
Please help me this infomation!
Thank you all

Stone of Destiny can only be used when actually choosing which class to awaken as. If you have already awakened, you cannot use it. This includes your dual class.