If a smaller pin is inserted in the forward fitting, pilots and hums will feel it as it has been written in a previous post.
If the normal pin is inserted, but not secured, as long as it stays in place, nothing could be felt, there is no play in the vertical/lift axis. but the second the pin moves out of the fitting in flight with roughly 11 tons of lift, the main rotor tilts backward and torn the epicyclic module.