You also can use plastic drywall anchors to avoid filling in old holes, re-drilling new holes or using larger screws. I then would put a SS washer on each screw to prevent it pulling thru the rub rail. A rubber mallet & a heat gun will help you inserting the center strip.
BTW: I see your in Cape Cod and your likely to be cold so a extra set of hands would help thus avoiding holding the heat gun in your mouth.
sequence: pinch bottom of the center strip insert flange into rail + pinch in top of center strip insert flange + hammer with mallet + pull center strip toward transom.....repeat=repeat=repeat..you might have excess to trim off when your done, never seems to be the same after removal.
