Unfortunately Khestral it may be something you have to play with. To address your question I'm fairly sure that's where his "Variance" step comes into play.
In the end though trial and error is sometimes the best teacher. Go thru the scaling tut, build out the piece you're most concerned with, and that will tell you for sure. Could it be a waste of materials? Sure, but it's better to sac some materials and gain some concrete knowledge on how to scale for your body.
Hope this helps!