Found a great way to keep seed shells off my floor when I let Kowhai and Tio free-roam the house! It was super easy - I just put the seed dish into a birdbath (minus the water)!
I got the idea from these seed feeders that claim 'no mess', but realized it was easy to replicate the double lip and opening that prevented my birds from flying off (the air pressure being the main catalyst for seed shells showering my floor) by just adding the bird bath.
So now I've got NO seed shells on my floor, so I'm chuffed about that as I have no carpets so once it's on the floor its on my feet. -_-
I'm in the middle of making a natural perch for them to stand on inside, but other than that, it's pretty easy and can go on the cage, or sit on a table.