I know it sounds as though the decision has already been made to leave the flexplate in there, but my professional advice to you is to change it out at the next possible opportunity. Elongated holes are never a good thing where rotational forces are concerned, and the eventual failure of the flexplate will occur much more rapidly the longer it is left in there. Imagine what type of repair you may be making after the flexplate fails while you are driving it, while it has a strong rotating force on it. Keep in mind your bellhousing is made of aluminum, Ive already replaced two of them, they arent that tough.