Tabulating up all of the thicknesses of the components for the watch, it seems like if everything is just stacked on top of each other, the thickness of the watch will be 18.75mm. Putting the backpack and trinket side-by-side, it comes out to a slightly more reasonable 16.75mm. The watch I currently wear is around 15 or 16mm, so it shouldn't be as unwieldy as a 2cm thick watch sounds. I'll see different ways I can arrange the parts once they arrive later today.