Here is a section out of the great website from Calame which is dialing in on the mortise in its French iteration, http://www.en.charpentiers.culture.fr/tr...hepiecesofwood# While there is evidence of the 30 mm mortise, personally I find no indication that drilling the mortise-side peg hole first is going on. Jon, I think what you have been taught is a deviation from normal or the technique as it is widely practiced even in France. Of course this is not to make a judgement of the rational you use to explain drilling the peg hole at the earliest possible moment.