Well, after about 6 weeks, I got the front element of my Summicron back. It looks very nice - like new... Actually, better than new, since it now has a better coating (more durable) than the original. 🙂
I took a few quick snaps on Efke 100, souped it in Rodinal, and the results are satisfactory. I tried several shots with strong backlight, and I'm pleased to say that in this regard the lens is much better now. I'll be shooting more with this lens, and will definitely have a better opinion whether anything has gone "wrong" with it during this procedure, but the first results look quite OK. In short, it was practically useless outdoors in bright light, whereas now I can't see any flaring and serious reduction of contrast...
Attached are two shots - first is one of the worst flare examples with this lens prior to recoating, and the second is my son, taken today with newly recoated front element, in roughly similar situation (strong backlight). Proof is in the pudding 🙂
Denis