I just have a few quick questions..

[Magnus]

And if the person making the tunic's "elbow span" is much less, due to their body size...guess what? You just dished out some bad advice, because now their tunic won't allow for enough movement at the upper leg.

And the elbow span idea (reference your last paragraph) is your concept, not mine. I've made over a dozen tunica at this point, and bare minimum you will require 30", depending on body size. As Dave mentioned, possibly more.