[matheweis]

It doesn't really work using VIX either. At the end of the day, using any constant across the options (measured volatility, VIX, etc.) you're assuming a flat volatility surface which you simply don't see in the real world.

A better approach might be to use some kind of avg volatility surface with VIX as a baseline, but even that leaves you with no sentiment.

For some strategies this might work well enough (e.g. a flat volatility surface implies a lot of 50/50 probabilities), but for any advanced historical analysis (which seems to be the scope of this post), you really need to have the price/IV of evry individual option.