There are going to be pretty different times for different films, so it is really tough to tell without your knowing what brand of film it is. You could certainly start at about 7 min, you will likely get something ranging from very good to marginally printable. For use as a one shot developer, D-76 is normally diluted 1:1, are you doing this or using as stock? If you are diluting the developer, I suspect you may be underdeveloping a touch at 7 min, but again it really depends on the film. Where did you get the film? That might help us identify it.