These are supports that allows you to connect the gopro bases with ram mounts.
I have inserted a sample stand and a support for a phone (huawey ale21).
printed 100% infill with PLA, I tried the PETG but it is too flexible so it does not close the balls well.
In the photos the white parts are printed in PETG the yellow and blue parts in PLA.
print the two ram parts with supports, then file them [not as i did of course ;-) ]

This thing was made with Tinkercad. If you can copy and edit the design to create your own support or base or whatever.

Edit it online https://www.tinkercad.com/things/9sL36ndZUp3

You can find all my models here, thank you who will appreciate with a download or with a like