Just went round Sunbury 9 hole in 44, which is 3 better than my best ever.
All because of more accurate drives and fairway wood shots which came about from 3 things.
1) better feet positioning apart and angle.
2) better ball position relative to feet (ie ball slightly more right of my left foot as you described)
3) shoulder rotation - I think before I was just using my arms. (saw this on you tube).
The first two were certainly helped by the kit, which I have taken down the range twice now.