These NPV Tests are the FDIC model which is NOT used by HAMP.
It give us clues but some of the input is secret as is the exact model.
As of 1/1/10 if denied there are supposed to send a letter showing the details or our input that went into the NPV but we don't know the secret assumptions in the model.
They are suppose to give you a phone to discuss any errors and have they have a 30 day window to respond and have to hold off sales. If they follow the directive which often servicers don't.
It is rumored to be "based" on the FDIC model but not the same.