First,find your smith and talk to them.Then,I suggest,when the cutting begins,sneak up on it a little at a time.
An old riflemaker did that with me,long ago.Take off an inch or 2,see how it hangs,then take a little more.I wouldn't make the first cut at 16 1/4
And,likely you will need to widen the sight notch,or narrow the blade,or get a smaller bead.