I remember someone saying they couldn't get it to work, but used blue foam to fill most of the 801 cart, with a "cap" of polyfill on top.
I suspect it's a question of getting the right compression -- if it's not squeezed a little, the blue foam just lets all the
juice drain out, but if it's squeezed too tight it doesn't wick.
You might try a strip of foam underneath, and a "cap" of blue foam positioned the other way, cut a little bit bigger than the actual room. But given the nooks and crannies of the 801 cart, the foam might not fill them all. Something more fibrous and flexible like polyfill or wool might be better.