If you will be riding in mountainous areas where there is a decent chance of cold rain, you might want something to keep your fingers warm. I was riding in MT last month and had to endure 2 25 mile descents in cold, wet weather. It even snowed a during one fo those descents. Consider at least a pair of light, polypro glove liners and maybe even something a bit warmer. You can always mail them home/to yoursef once that likelihood diminishes. And maybe arm and leg warmers.
And +1 for what mm718 wrote regarding some items noted. While I don't cary electronics other than a dumb phone and charger, I do put my toilet items in a freezer bag for the very reasons he notes. 1 SS shirt. 1 LS shirt. Convertible pants. Recently bought a very light pair from North Face. Jeans are a brick compared to them. For me, it's two pair of undies (brtiefs so they are light and not bulky.