As you can see by the “T” shape the rear portion contains a series of 3/8″ threaded holes that allow you to spin-on our threaded weights to counter act heavy lenses/mattebox. By doing this you are also adding bottom counterweight to help counter act top heavy camera builds. This might eliminate the need for arm extensions and a tilt arm extension!
Feel free to watch the tutorial for the PRO Dovetail. I used a Ronin but all the same applies to MoVI of course. Long and detailed, but you will get the most out of your new investment.