Jim, That piece is called screw cover or insert. Many colors available, white, black, beige. Yes they shrink. On our Full body paint both sides have pulled tight and have started to come out of the trim. Since the pieces are painted I had to pull them to their original positions in order for the paint lines to match up. I used a clear sealant underneath the trim in several places and used the blue or green painters tapes to hold them in place until the adhesive cured. If stretched tight when applying they will come out of the track for sure. Happens to almost all RVs at one time or another. The hot sun will soften the trim, traveling at 65 mph blows under the trim and there you go. Cold causes the trim to tighten and shrink also. Difficult balance for sure.
Chris & Maria
2012 36RL, Full Body Paint, Dual Awning, Dual a/c, Splendide Combo, Fisher Paykel dishwasher, 6.5kW Onan, Goodyear G614's. 2015 F550 6.7l, 4X4, Lariat, CC, 176" WB, Long Box, B&W Companion