Groundhog are you using fan jets ?
I have 2 harris poles now Ian, the one with the extension on it has fan jets, but the one that I was using clampless has pencil jets. No particular reason for this, its simply that they were the brushes I managed to salvage from my old poles. I have always used pencil jets in the past, but have recently started using the brush with fans, to be honest I like them both, I'm still undecided as to which I prefer. The only possible downside to fans I have found is that mine seem to get blocked more easily, apart from that I like them.