how do you set up on the approach? here is one that i try, when i want to play straighter.
normally when i want to open up the lane, i will move my heels left, so my body is turned to the right a little bit. this helps so i don't have to open up my body as much, to get the ball right.
now when i want to square up, i will move my toes to the left instead, so my body is facing the left a little more. what this does for me, is when i bring my ball back, i am more square at the release point. and even if you do open up a tad, you won't throw it out to the right as much, so you will hopefully have a little more area to play with, and not worry about going past the headpin.
hope this helps and good luck!