I was modeling the STT trade in TOS and everything looks fine until I introduce IV increase. I would expect IV to increase in a case of a 10+% sell-off. With the IV increase of 10 points, the value of the STT is cut in half. This is for a well aged position, so a new position would be a loser anyway. This does not look like a good hedge.
I have noticed that presentations about STT definitely ignore ( if not refuse) to include the IV increase. I watched a number of them and every time all modeling is done without taking IV into consideration.
Am I missing something in the TOS model?