The open stance forehand has been maligned for quite some time, in favor of stepping into the ball.
This is an illusion, contrary to the best of human performance.
The most powerful, efficient and most effective kinetic chain starts rotation on the same side foot as your hitting hand, like in Martial Arts.
Rather than pushing forward, the hand pulls from the racquet, which accentuates its acceleration, as in a whip.
The left foot, for a right hander, leaves the ground during this forehand, helping pull across and backwards in an arc.
Instead of hitting on the line of the ball, as predominantly taught, realize that the best strokes are rotational.
One intends not only to apply rotation to the ball, as in topspin, but also to apply rotation to the body, maximizing its most efficient effort to power the ball and to have it land in the court.
Two-handed backhands are similarly pulling from the racquet, most efficiently loading on the left foot and open-stance. Serena and Venus Williams are a prime example of this technique.
The one-hander, slightly different, pulls across and backwards with your back.
Try this technique and you’ll see great improvement, not only to your power and topspin, but also in your ability to get your shot, no matter how hard, to land within the court.
The top pros, in their best days, do it easily. Roger Federer, who has my book and Master Strokes videos since April 2005, is back to his old days of success on groundstrokes, supplemented with a persistent attack.
One word of wisdom, here, track the ball closely with your hand/hands, then pull across, to avoid mishits.
Watch my videos/DVDs. For a small investment, you’d be on top of your world!