What you might want to do is buy a good lens (Edmund Scientific's Plummer Series??) that meets the spec's of the Reference element for shape and test against a known good mirror and repolish the reference side if there are problems with the surface. Rotating the lens will show differences between the tests and thus show what the true surface of the lens is. Peter told me (when I bought mine) that the back surface isn't anywhere near as sensitive to making errors. Good Luck! Patience is necessary when working with this problem.