I saw a video of a guy who used his Moerman channel and rubber in an Ettore Contour Plus handle, (the spring loaded one).
He reckons it's fantastic, best he's ever used.
So I went a bought one, just for the hell of it.
I don't know why, but it works really well; no more lines.
Also looking at PNB, I now add soap to the mop, not in the bucket. That works better too.