The cutouts can be filled with lead or steel shot, or plaster, etc. to give the base some extra weight. I used lead pellets and filled the remaining space with black tinted epoxy.
The author remixed this model.
I wanted to use taller LED profiles, and so needed a way to make the base heavier and thus better suited for longer LED profiles. I created cutouts in the original design to allow filling with something heavy - plaster, steel pellets, lead pellets, etc,. , and extended the sleeve that holds the v-profile to give the longer aluminum profiles some additional support.
I also added a recess in the electronics cover where an INMP411 digital mic can be placed, for those people who want a sound reactive controller.
STEP file included for those who want to modify further.