I stuff all my filters to replicate the Aquaclear style. I have a lot of Aquaclears, too.
Sponge at the bottom. (Actual Aquaclear sponges)
Quilt batting on top of the sponge.
Nylon stocking of loose media that varies with the tank: Peat for soft water, coral sand for hard, and ceramic bio noodles or lava rock. I can cut knee-hi stockings into 3 media bags for small filters or 2 larger bags for the bigger filters.
I cut the plastic frame from the cartridges about 1.5" high so it just sits in its grooves at the top of the filter, and keeps the media from falling into the tank.