Mantus Marine Rail CLAMP Set (Clamp Set (1" Rail))

Has the problem of the item having the potential to come apart when attaching/detaching been rectified? I won't buy it unless it has.

Can the black mounting surface be removed (unscrewed) from the mount, if so, what are the threads on the mount itself?

Could these be used on square railing or just round?

What size screws do you use for the AMP holes?