Not sure why the worry. 95% of the time, a 15 yard DPI is going to be a first down anyway. There are two situations where it will be an issue: more than 15 yards to gain to reach the LTG, and DPI in the end zone when the goal line if the LTG.
On the first, you are still going to get to repeat the down, and there are VERY few 15+ yard passes on long yardage situations anyway. In HS football, a completion where the catch is more than 15 yards downfield is still the minority of pass plays, so on DPI, the offense is still going to get 15 yards, and they are going to get the down again. They aren't going to be that upset.
The one tricky one is going to be 3rd and less than 10 with the goal line the LTG. In those cases, it may actually be worth the DPI if there is a good chance the ball will be caught.
But for the vast majority of the time, this is a non-issue.