This is what i have on mine, clamps nice and tight, no movement and allows for full collapse of the stock..although i cannot really attest to its use for shortly after i put it on, i read after that the comps i enter don't allow the use of slings so, it just sits looking pretty. They have a selection check out the page. Not that its any different to the ones you posted.
I have the Midwest Industries mount (MCTAR-30), and it works very well. You will lose one position on the adjustable stock, but that was something I can easily live with. The mount seems to be a well made part.
I choose to use the magpul single point picatinny mount. I use it up high in front of my rear flip up and it keeps me from catching the rifle in the you know whats....