The swing length is when your left arm is parallel to the floor (9 o’clock). Shaft angle should be approximately butt end pointing down to the ball.
Swing through the ball to a finish position with your arms roughly at around 3 o’clock. your hips and feet will have followed through approx 2/3 of full.
To add extra distances to your pitching control, practice 8 o’clock to 4 o’clock and 10 o’clock to 2 o’clock.
Practice this position swing using your PW, GW, SW & LW. Don’t be too hasty in measuring the distances, Once the ball grouping is getting tight that is the time to measure. Also practice holding at the base of the grip which will reduce length of distance by approx 5 yards.
It is worth mentioning at this point that swing tempo is very important to control distance, the same length swing with different acceleration speeds will result in different distances, I do believe you will find a tempo that works best for you.