Steve: I agree with everything save one: "3.The RTD greeks are always vol smile greeks ... changing to IIV in TOS never flows through to RTD greeks." <-- Untrue, Unless you happened to test with TOS screwed this up previously! I have observed that the RTD connection seems to need re-establishing after tweaking the TOS setting for Smile VS IIV. -- If your re-establish the RTD links after the TOS change (and after the change is observed within tos), then the RTD reflects the new IV setting results. However, I agree with your final conclusion that using the TOS IV is a sloppy approximation of IV. Your paper aids in providing a much better approximation of IV.