Ok, I owe mavgi and others an apology. I've been going around talking about how people are "hacking away" and "mangling" their impellers. But I also gathered the material and ordered an extra impeller, and hacked myself (finger) and the old needlewheel.
Last night tried enkamat and the synthetic steel wool (BTW: no need to get that ... large pet chains carry the scrubbie for cleaning the glass, and it's the same stuff and cheaper) in turns.
Not bowled over. Air from 5-7lpm up to 7-10lpm, identical on each.
BUT I wasn't too careful with the enkamat. I cut new pieces, careful to cut larger than needed and in squares. Used scissors to carefully open a small hole in the center of each to slide over the piece on the needle-less wheel. Used smaller zip ties and was careful not to scrunch or pull the enkamat.
POW! 15lpm steady. I can't see well into my G5 ... dirty on outside (calcium/salt). But the foam is unbelievable even in 5min and the hiss from the tubing is tremendous. No way the G5 could handle 2 of these I guess. Lowered water in chamber substantially. We'll see how it skims.
But I can't see how it can be anything but a tremendous improvement.
If it doesn't hold up over time, then back to the stock needlewheel. I do have my doubts that this stuff may just disintegrate...