My #983 with a new Ensign Spars deck has the T-shaped plastic piece attached to the deck with small stainless sheet metal screws. These have held well, and are certainly easier to remove if you have to get at the hull/deck joint at some future point.
Last I checked (just now) the link to the rub rail installation video at Ensign Spars does not work.
I recently removed all but the stern end of my rub rail to fix a leaking hull/deck joint. Getting it back on after cleaning was not a walk in the park. You'll need a heat gun to allow the rail to stretch the required length, three feet at a time. I did this on a 60 degree day, maybe easier in the summer sun.
Dick Beverly
Tracy #983
Milwaukee WI