I have the same issue and i can never seem to get more than 5 or six drops into the cart with the ptb...and I rolling too tightly? If I am then the ones I roll loosely leak all over the place....I must be doing something wrong...they work really well when they work.
you do have to experiment on the PTB's to find just the right amount and how to roll/plug/shred. i have been doing it for 2 weeks now and just cant seem to find the right combo but like everyone says, it is better than polyfill.
i tried a thin sheet of Fluval wrapped in PTB and it was a huge NOGO! so far the best that i have come up with on my 401 is the half PTB folded in half with a single tiny fold along the top and shreded lower half with the shredded end in the cart first. i have seen that the liquid tends to stay in the folded parts and the shredded end keeps the folded end on the atty really well.