Well, after an entire day reworking the periscope model (you have no idea how many useless polygons are there
) and a few hours trying (and failing) to achieve a nice metal look, I've made the periscope background. The size of the reticule is almost the same, just a bit smaller so that the real marking layout should fit nicely. On 16:9 resolutions it will take the same space on screen but you'll be able to see a few more things to the sides. Here's a pic (1600x1200) made in photoshop so don't mind the blurry low rez orders bar:
