deffinatly stitch past the line stoping point and as for getting a good point and not cutting it off. you want to stitch a thread or two to outside of the point. and it really depends on how you are turning the fabric that will give you how much if the point is turning you might need an extra thread but if the new fabric is what is being turned then you will probably only need a thread or two to the outside of the x in the point. this is how I do it and it works well for me.