Tumbling chaeto is really overrated (and unnecessary). If you have a setup that can grow chaeto well, eventually you'll have a mass that is big enough that tumbling is impossible to achieve.
If your concern is providing enough light/spread to more of the chaeto, consider mounting a panel to the side as well. I do that myself. I mount two of these panels on two sides of my fuge, but I'm sure a light the top and one of these from a side would work just as well.
I use this light panel mounted to the side of my glass sump with 3M Command Strips. If you have an acrylic sump, you might want to mount with something that will provide a little more space between the sump and panel as acrylic doesn't do well with heat.
https://www.amazon.com/gp/product/B01M8HJZYU