I was doing something similar, but I finally made myself a new window with a mag vent setup. I used 3 layers of acrylic, which was about the same thickness of the window that was in the frame previously. Then I took a vent cover off of the previous vent I was using and created a multi-layer acrylic adapter to mount it to my new window. The “window” isn’t completely clear because the weld-on I used to bond the layers makes it look like there is water stuck in the window, and the window was wider than the GF basic can cut, so I had to come up with a way to layer and extend the acrylic, but overall it’s much nicer than the plywood frame I had in there before, and adds back some natural light in the basement.
