How far you go with your backhand racquet preparation on a drive depends on the situation you are in. A difficult service return might mean that you need to abbreviate your backswing, creating a blunted drive. Of course, you could choose to block or chip the shot. But how far should your racquet go back for a no-compromise drive?
A good exercise is to make sure that the racquet tip can be seen by your opponent when fully loaded. That way you can be sure that you are set up well enough to generate some serious backhand power!
As you can see from Dementieva’s racquet preparation, she is in the classic loaded position showing her opponent her racquet tip. Notice also that her racquet head is higher than the grip in preparation for the racquet drop on the follow-through. Obviously she needs to get the raquet head lower than the ball to lift up with her heavy topspin, but if she took the racquet straight back low and then lifted up, she would lose both rhythm and power in her backhand shot.
Dementieva displays superb organisation and comfort for the shot. Everything is tied in together to accomplish this. The movement, the preparation, the concentration and the follow-through, all work together as one.