I apply Scott Fawcett´s strategy approach since 2016. The number 70 is the dispersion for a tour pro at 270 yards carry were 90-95% of their golf shots ends.
In your 15 ball test, take the 2nd fardest away from the target. That´s your dispersion divided by 2. Apply scott´s strategy with that number, and not 70.
As an example mine is 80 yards (40 left, 40 rigth) wide at 270 yards carry+roll.