Rodger...
I never found it to let dust through the filter to much, really, it is the seal around the fill tube that wasn't really up to the job and as the mesh filter clogged, which I felt is the thing that blocks the airflow, not the "high density paper filter". With a heavy amout of airflow relentlessly blowing into the Permabag, but couldn't escape easilly as the air was restrickted, the System started to be pushed away from the rubber seal on the fill tube and the dusty air started to leak into the Permabag housing and then went around the sides and into the air, so ultimately, quite a bit of dust lined the machine and went back into the room!
The bagged versions were a LOT better than the Permabag varitation, but it is a shame that Turbopower Freedom was so bad, because it is quite a sexy looking cleaner if you ask me.
Here is a video I made a while ago using it to pick up flour! as you can see, when I went over the edge of the stair ledge, just violently blew out of the sides of the Bag housing.