I gave up on cups. For me, they were inefficient and anything I tried clogged up too quickly. Went to mesh socks in lieu of the cups or the felt socks and I've been much happier.
When I ran the cups, I put ceramic bioballs on the bottom, followed by a sponge disk. The disks would clog up quickly and too much waste got through, making my DT water look cloudy all the time.
I then tried floss on top, which clogged up even quicker and made my skimmer go nuts for up to a day after adding new floss.
Then I tried a sponge block on top of a dispersion trickle plate over the cups, which also clogged up very quickly and made my sock chamber overflow constantly.
I also tried media bags inside the cups, and the bags would also clog up quickly.
This is on a Trigger Systems Sapphire 44 sump, using triple 4" cups/socks.
The mesh socks keep my water looking crystal clear and I can go over a month with out having to swap them out.