Bumping up from 19 to 20 was a change I made a few days ago, so I'll try at 19 and see if that helps at all.
I reduced my intensity by 2 on all cards running more than 18 (20 to 18, 19 to 17, 18 to 16) and that really helped a lot. Was getting ~15%, now averaging ~6-7%, and that was before Terk fiddled with the settings today.
what effect did that have on your KH/s? is the reduced reject rate proportional to the reduced Kh/s? i'd be trying to keep my KH/s as high as possible.