At least Steve C thinks Clamcleat "Aero" bases are legal. As I've mentioned before, the rule text doesn't specifically mention cleat accessories like that. Is something with four holes a "ring"?
The two pictured systems differ really only in to which part (moving or non) of the line the cleat is attached. The other also has a shackle as an aft fairlead.
The picture with the supposedly-approved alternatives to the shackle includes the Ronstan Shock Block, which stretches the definitions of both "block" and "ring".
No word on which cleat features/accessories are allowed.