In that case, just adopt the NCAA rule on DPI. Spot, 15, or 2 makes sense, because the ball is at the spot of the foul if the pass was not a long one, 15 yards would be a major deterrent on long passes, because that would give A a free series (the automatic 1st down provision addresses those cases where 15 yards would not affect the next series, whether on 2nd and 16+, 3rd and 16+, or inside the 30 yard line, where half the distance enforcement reduces the possible distance), and the 2 yard line provides a consistent spot for fouls on passes near the goal line (specifically, a pass when the previous spot is between the B17 and B2 inclusive, with a foul on or inside the B2). If spot, 15, or 2 is a simple enough mnemonic for new NCAA officials, NFHS officials would also be able to pick up on it.