.... Does any one use these ?
These kellets can definitely help with holding, by keeping the angle of pull on the rode as low as possible.
I don't buy it. The vast majority of kellets are to light to do anything in a real blow. And that is when you need them.
With the correct anchor set up I think they are a waste of time.
Unless they are very heavy. And then they are a PITA to deal with. And could become a danger to those handling the anchor gear.