This is me personally speaking, I am not a GML and my opinion is just that, an opinion from a fellow officer builder. I do believer your tunic is going to come up a few inches short when all is said and done.
However, with that said, let's not get all sad faced yet! I actually think there is a bit of a silver lining here for your build! If we can get you that correct sized poncho, it will cover the tunic completely and in my opinion drastically improve your build IMHO. From my understanding, and Von can chime in here... your given the approval from what can be seen, not what's underneath. That poncho will cover these issues and looks a heck of a lot better, at least too me. Just some food for thought.