We used the Freefly Ember on the RS3 Pro and it barely fit. Is it also possible to mount the Pixboom with a V-mount battery on it? I think the RS4 Pro is slightly bigger, so it should fit there?
Have you tried it yet?
Interesting question! I believe the RS4 Pro should work perfectly! For example, the Arri Alexa Mini can be mounted without any issues: https://www.youtube.com/watch?v=T8JSViHZDk8