This cast was not destined for an orthotic, so can't really say. I was emphasising the practicality of dorsiflexing the FIFTH met and plantarflexing the first because originally this video was a response to Jeff's query as to whether it was possible to dorsiflex the 5th met when casting in foam.
If I were to be treating this patient it would depend a great deal on what materials I was using and what I was treating her FOR. My favourite is something called Therrox which is much more forgiving of medial wrap than polyprop so I would not need a great deal of medial expansion with that. Or, If I was using poly, I'd expand the medial arch in the foam. So far as arch FILL is concerned, it would depend on things like supination resistance, axial location and what I was trying to acheive. Either way, I'd get the level I want from the amount of plantarflexion in the 1st met and expand medially rather than go for 100% plantarflexion and then fill the arch afterward.