We are an OCC bank and had a similar situation a couple of years ago. Our EIC (Central Region) indicated there is no exception or exclusion for the stressed value of the property.
So if it's a $100M property that your buyer is purchasing for $20M, your LTV calculation relies on a $20M value. No fun, but hopefully you have room in your SLTV calculation to make the loan if it's a good customer.
About six months down the road, you would be able to rewrite the loan into a conforming position on paper as well as in reality.
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