To start with you make your own front curve even if its high index. You can hard coat that surface.Use plastic for the abby value and from the front curve say -2.00 or three or four to get the front curve to make a full field. I've done bi-concave for the rx part and a bi-convex for looks on rx's over -30.00.To me this is fun.I love a challenge and turn nothing down until I have exhausted all possibilities at my own expense with many blanks. And I love to talk optical problems.Call me at winchester Optical 607-73-44251 It's Bill Brown Special surfacing.