darkroomsource,
If your plane has a glide ratio of 1:6 at a speed of 65 kt, and you maintain that speed against a 15 kt headwind, your glide ratio relative to ground will be 1:4.6 . So don't worry, you will still make your 45 degree cone, despite your performance being less than optimal.
Isnt that what I wrote?
But, if you change the glide speed, based on the discussions above, and on other places, then you will not be assured of making that location.
Again. Best glide speed, which is the best lift to drag ratio, is NOT affected by the wind speed. Best Glide Distance, is affected by the wind speed.