Trying to improve backswing

Hi all

I've been trying to tinker with my technique in a bid to improve my game, so I've watched a few top players on the internet and I've noticed on their backswing they bring their cue almost back to their thumb on their bridge hand, particularly on power shots. This is really noticeable in O'Sullivan's and Ricky Walden's backswing. I've tried to do the same but my timing goes right out of the window and miss the object ball altogether! I don't have too much trouble with screwing the ball as I follow through well but I'm struggling with the backswing (along with the final pause). Has anyone got any hints on how I can improve this?

Thanks for any replies!

Trying to improve backswing