Your position at the top is not as important as what you are doing with your rotation of the hips and shoulders. So don't worry about where you club is at the top. Make the big rotation through the ball and if you are getting a good release of the hands, you are good.

Flexability will always help, and you should always work on that with streaching before and after rounds and practice sessions. But, if you are finding that you want to get to the top, do not get there by breaking the leading arm (as you mentioned). that is your extension of the club (the lever arm in the swing) and breaking it will shorten the length of your arc which will take away force at impact. Keep it long and extended, and rotate that big beautiful body that can create a lot of power for you. Make sure the hands don't get overpowered. If you start to slice it, your body is usually getting too much for the hands and they can start to lag behind. So ease up on the body rotational speed a little and that will allow the hands to catch up and get square again.