With the ship mast experiment, wouldnt it demonstrate relativity more than projectile motion as dropping a ball isnt too much of a projectile motion is it, even with people on shore seeing the ball following a parabolic path, would you have to say that he assumed that projectile motion has a constant horizontal motion and a changing vertical motion? although the experiment doesnt prove the projectile motion is consisted of those components, it just proved something with constant Vx and a changing Vy follow a parabolic path.
What's the ball rolling thing, inclined plane experiment or something like that?